diff --git a/gtk2_ardour/about.h b/gtk2_ardour/about.h
index a99294de8f..2ccd86ec75 100644
--- a/gtk2_ardour/about.h
+++ b/gtk2_ardour/about.h
@@ -17,8 +17,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_gtk_about_h__
-#define __ardour_gtk_about_h__
+#pragma once
 
 #include <gtkmm/aboutdialog.h>
 
@@ -39,4 +38,3 @@ private:
 	static void launch_homepage (AboutDialog& about, const Glib::ustring& website_url);
 };
 
-#endif /* __ardour_gtk_about_h__ */
diff --git a/gtk2_ardour/actions.h b/gtk2_ardour/actions.h
index a805604cfc..ab2cfc003d 100644
--- a/gtk2_ardour/actions.h
+++ b/gtk2_ardour/actions.h
@@ -19,8 +19,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_gtk_actions_h__
-#define __ardour_gtk_actions_h__
+#pragma once
 
 #include <vector>
 
@@ -66,4 +65,3 @@ namespace ActionManager {
 }
 
 
-#endif /* __ardour_gtk_actions_h__ */
diff --git a/gtk2_ardour/add_route_dialog.h b/gtk2_ardour/add_route_dialog.h
index 542d8f8f84..1111806f24 100644
--- a/gtk2_ardour/add_route_dialog.h
+++ b/gtk2_ardour/add_route_dialog.h
@@ -23,8 +23,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_add_route_dialog_h__
-#define __gtk_ardour_add_route_dialog_h__
+#pragma once
 
 #include <string>
 
@@ -181,4 +180,3 @@ private:
 	void name_template_entry_deletion (int, int);
 };
 
-#endif /* __gtk_ardour_add_route_dialog_h__ */
diff --git a/gtk2_ardour/add_video_dialog.h b/gtk2_ardour/add_video_dialog.h
index a53a4241d8..7d1c108597 100644
--- a/gtk2_ardour/add_video_dialog.h
+++ b/gtk2_ardour/add_video_dialog.h
@@ -15,8 +15,7 @@
  * with this program; if not, write to the Free Software Foundation, Inc.,
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
-#ifndef __gtk_ardour_add_video_dialog_h__
-#define __gtk_ardour_add_video_dialog_h__
+#pragma once
 
 #include <string>
 
@@ -126,4 +125,3 @@ private:
 	bool loaded_docroot;
 };
 
-#endif /* __gtk_ardour_add_video_dialog_h__ */
diff --git a/gtk2_ardour/ambiguous_file_dialog.h b/gtk2_ardour/ambiguous_file_dialog.h
index 94a821b726..9e5728706a 100644
--- a/gtk2_ardour/ambiguous_file_dialog.h
+++ b/gtk2_ardour/ambiguous_file_dialog.h
@@ -19,8 +19,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_ambiguous_file_dialog_h__
-#define __gtk_ardour_ambiguous_file_dialog_h__
+#pragma once
 
 #include <gtkmm/radiobutton.h>
 #include "ardour_dialog.h"
@@ -38,4 +37,3 @@ private:
 	bool rb_button_press (GdkEventButton*);
 };
 
-#endif // __gtk_ardour_ambiguous_file_dialog_h__
diff --git a/gtk2_ardour/analysis_window.h b/gtk2_ardour/analysis_window.h
index 3a930013c8..d29b1aa617 100644
--- a/gtk2_ardour/analysis_window.h
+++ b/gtk2_ardour/analysis_window.h
@@ -17,8 +17,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_analysis_window_h__
-#define __ardour_analysis_window_h__
+#pragma once
 
 #include <glibmm.h>
 #include <glibmm/refptr.h>
@@ -116,5 +115,3 @@ private:
 	friend class FFTGraph;
 };
 
-#endif // __ardour_analysis_window_h
-
diff --git a/gtk2_ardour/ardour_dialog.h b/gtk2_ardour/ardour_dialog.h
index e3bf268176..a45d4d8de8 100644
--- a/gtk2_ardour/ardour_dialog.h
+++ b/gtk2_ardour/ardour_dialog.h
@@ -19,8 +19,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_dialog_h__
-#define __ardour_dialog_h__
+#pragma once
 
 #include <gtkmm/window.h>
 #include <gtkmm/dialog.h>
@@ -67,5 +66,4 @@ private:
 	static sigc::signal<void> CloseAllDialogs;
 };
 
-#endif // __ardour_dialog_h__
 
diff --git a/gtk2_ardour/ardour_http.h b/gtk2_ardour/ardour_http.h
index b4d8439549..444749af45 100644
--- a/gtk2_ardour/ardour_http.h
+++ b/gtk2_ardour/ardour_http.h
@@ -16,8 +16,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_http_h__
-#define __gtk_ardour_http_h__
+#pragma once
 
 #include <curl/curl.h>
 #include <string>
@@ -98,4 +97,3 @@ std::string http_get (const std::string& url, bool with_error_logging);
 
 } // namespace
 
-#endif /* __gtk_ardour_http_h__ */
diff --git a/gtk2_ardour/ardour_ui.h b/gtk2_ardour/ardour_ui.h
index b91b174f2a..f73aeb3b5c 100644
--- a/gtk2_ardour/ardour_ui.h
+++ b/gtk2_ardour/ardour_ui.h
@@ -30,8 +30,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_gui_h__
-#define __ardour_gui_h__
+#pragma once
 
 #include <time.h>
 
@@ -952,4 +951,3 @@ private:
 	PBD::ScopedConnectionList clock_state_connection;
 };
 
-#endif /* __ardour_gui_h__ */
diff --git a/gtk2_ardour/ardour_window.h b/gtk2_ardour/ardour_window.h
index 2102eaae9e..8746811711 100644
--- a/gtk2_ardour/ardour_window.h
+++ b/gtk2_ardour/ardour_window.h
@@ -16,8 +16,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_window_h__
-#define __ardour_window_h__
+#pragma once
 
 #include <gtkmm/window.h>
 
@@ -54,5 +53,4 @@ private:
 	void init ();
 };
 
-#endif // __ardour_window_h__
 
diff --git a/gtk2_ardour/audio_clip_editor.h b/gtk2_ardour/audio_clip_editor.h
index 3c3b8c295c..9782bd7f74 100644
--- a/gtk2_ardour/audio_clip_editor.h
+++ b/gtk2_ardour/audio_clip_editor.h
@@ -17,8 +17,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __audio_region_trimmer_box_h__
-#define __audio_region_trimmer_box_h__
+#pragma once
 
 #include <map>
 
@@ -221,4 +220,3 @@ private:
 	void zoom_out_click ();
 };
 
-#endif /* __audio_region_trimmer_box_h__ */
diff --git a/gtk2_ardour/audio_clock.h b/gtk2_ardour/audio_clock.h
index afea1f9d4a..b697c0b123 100644
--- a/gtk2_ardour/audio_clock.h
+++ b/gtk2_ardour/audio_clock.h
@@ -23,8 +23,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __audio_clock_h__
-#define __audio_clock_h__
+#pragma once
 
 #include <map>
 #include <vector>
@@ -259,4 +258,3 @@ private:
 	PBD::ScopedConnection tempo_map_connection;
 };
 
-#endif /* __audio_clock_h__ */
diff --git a/gtk2_ardour/audio_region_editor.h b/gtk2_ardour/audio_region_editor.h
index 52fad5afe8..095da2c19f 100644
--- a/gtk2_ardour/audio_region_editor.h
+++ b/gtk2_ardour/audio_region_editor.h
@@ -20,8 +20,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_audio_region_edit_h__
-#define __gtk_ardour_audio_region_edit_h__
+#pragma once
 
 #include <map>
 
@@ -106,4 +105,3 @@ private:
 	CrossThreadChannel _peak_channel;
 };
 
-#endif /* __gtk_ardour_audio_region_edit_h__ */
diff --git a/gtk2_ardour/audio_region_operations_box.h b/gtk2_ardour/audio_region_operations_box.h
index b8fc6241f1..01d0b29d3b 100644
--- a/gtk2_ardour/audio_region_operations_box.h
+++ b/gtk2_ardour/audio_region_operations_box.h
@@ -17,8 +17,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __audio_region_operations_box_h__
-#define __audio_region_operations_box_h__
+#pragma once
 
 #include <map>
 
@@ -72,4 +71,3 @@ private:
 	void normalize_button_clicked();
 };
 
-#endif /* __audio_region_operations_box_h__ */
diff --git a/gtk2_ardour/audio_region_properties_box.h b/gtk2_ardour/audio_region_properties_box.h
index c1399c6441..131be9fae9 100644
--- a/gtk2_ardour/audio_region_properties_box.h
+++ b/gtk2_ardour/audio_region_properties_box.h
@@ -17,8 +17,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __audio_region_properties_box_h__
-#define __audio_region_properties_box_h__
+#pragma once
 
 #include <map>
 
@@ -88,4 +87,3 @@ private:
 	ArdourWidgets::ArdourButton stretch_selector;
 };
 
-#endif /* __audio_region_properties_box_h__ */
diff --git a/gtk2_ardour/audio_region_view.h b/gtk2_ardour/audio_region_view.h
index 9494f51e04..e4765028bb 100644
--- a/gtk2_ardour/audio_region_view.h
+++ b/gtk2_ardour/audio_region_view.h
@@ -21,8 +21,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_audio_region_view_h__
-#define __gtk_ardour_audio_region_view_h__
+#pragma once
 
 #ifdef interface
 #undef interface
@@ -253,4 +252,3 @@ private:
 	PBD::ScopedConnection _region_fx_connection;
 };
 
-#endif /* __gtk_ardour_audio_region_view_h__ */
diff --git a/gtk2_ardour/audio_streamview.h b/gtk2_ardour/audio_streamview.h
index fb8b616a69..ffcc6dbfce 100644
--- a/gtk2_ardour/audio_streamview.h
+++ b/gtk2_ardour/audio_streamview.h
@@ -19,8 +19,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_audio_streamview_h__
-#define __ardour_audio_streamview_h__
+#pragma once
 
 #include <cmath>
 #include <list>
@@ -95,4 +94,3 @@ private:
 	bool outline_region;
 };
 
-#endif /* __ardour_audio_streamview_h__ */
diff --git a/gtk2_ardour/audio_time_axis.h b/gtk2_ardour/audio_time_axis.h
index a0dc6b6d41..31ef662c40 100644
--- a/gtk2_ardour/audio_time_axis.h
+++ b/gtk2_ardour/audio_time_axis.h
@@ -21,8 +21,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_audio_time_axis_h__
-#define __ardour_audio_time_axis_h__
+#pragma once
 
 #include <gtkmm/table.h>
 #include <gtkmm/button.h>
@@ -97,5 +96,4 @@ private:
 	void update_control_names ();
 };
 
-#endif /* __ardour_audio_time_axis_h__ */
 
diff --git a/gtk2_ardour/automation_controller.h b/gtk2_ardour/automation_controller.h
index 90b1c73be6..9840cd0f72 100644
--- a/gtk2_ardour/automation_controller.h
+++ b/gtk2_ardour/automation_controller.h
@@ -19,8 +19,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_gtk_automation_controller_h__
-#define __ardour_gtk_automation_controller_h__
+#pragma once
 
 #ifdef YES
 #undef YES
@@ -108,4 +107,3 @@ private:
 };
 
 
-#endif /* __ardour_gtk_automation_controller_h__ */
diff --git a/gtk2_ardour/automation_region_view.h b/gtk2_ardour/automation_region_view.h
index 8e3f0d11ce..789ba75921 100644
--- a/gtk2_ardour/automation_region_view.h
+++ b/gtk2_ardour/automation_region_view.h
@@ -18,8 +18,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_automation_region_view_h__
-#define __gtk_ardour_automation_region_view_h__
+#pragma once
 
 #include "ardour/types.h"
 
@@ -95,4 +94,3 @@ private:
 	PBD::ScopedConnection               _mouse_mode_connection;
 };
 
-#endif /* __gtk_ardour_automation_region_view_h__ */
diff --git a/gtk2_ardour/automation_selection.h b/gtk2_ardour/automation_selection.h
index 3aaf2bd2b5..eafc68682e 100644
--- a/gtk2_ardour/automation_selection.h
+++ b/gtk2_ardour/automation_selection.h
@@ -16,8 +16,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_gtk_automation_selection_h__
-#define __ardour_gtk_automation_selection_h__
+#pragma once
 
 #include <list>
 
@@ -40,4 +39,3 @@ public:
 	}
 };
 
-#endif /* __ardour_gtk_automation_selection_h__ */
diff --git a/gtk2_ardour/automation_streamview.h b/gtk2_ardour/automation_streamview.h
index e79b56aafe..97aba63793 100644
--- a/gtk2_ardour/automation_streamview.h
+++ b/gtk2_ardour/automation_streamview.h
@@ -19,8 +19,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_automation_streamview_h__
-#define __ardour_automation_streamview_h__
+#pragma once
 
 #include <list>
 #include <cmath>
@@ -86,4 +85,3 @@ private:
 	ARDOUR::AutoState _pending_automation_state;
 };
 
-#endif /* __ardour_automation_streamview_h__ */
diff --git a/gtk2_ardour/automation_time_axis.h b/gtk2_ardour/automation_time_axis.h
index 4000bbc0ed..06efc599a5 100644
--- a/gtk2_ardour/automation_time_axis.h
+++ b/gtk2_ardour/automation_time_axis.h
@@ -23,8 +23,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_gtk_automation_time_axis_h__
-#define __ardour_gtk_automation_time_axis_h__
+#pragma once
 
 #include <list>
 #include <memory>
@@ -242,4 +241,3 @@ private:
 	int set_state_2X (const XMLNode &, int);
 };
 
-#endif /* __ardour_gtk_automation_time_axis_h__ */
diff --git a/gtk2_ardour/axis_view.h b/gtk2_ardour/axis_view.h
index d63a410e9d..a6e8eec919 100644
--- a/gtk2_ardour/axis_view.h
+++ b/gtk2_ardour/axis_view.h
@@ -21,8 +21,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_gtk_axis_view_h__
-#define __ardour_gtk_axis_view_h__
+#pragma once
 
 #include <list>
 #include <boost/unordered_map.hpp>
@@ -137,4 +136,3 @@ protected:
 	mutable boost::unordered_map<std::string, std::string> property_hashtable;
 }; /* class AxisView */
 
-#endif /* __ardour_gtk_axis_view_h__ */
diff --git a/gtk2_ardour/bbt_marker_dialog.h b/gtk2_ardour/bbt_marker_dialog.h
index 376a725031..2dfd101a0b 100644
--- a/gtk2_ardour/bbt_marker_dialog.h
+++ b/gtk2_ardour/bbt_marker_dialog.h
@@ -16,8 +16,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_gtk_bbt_marker_dialog_h__
-#define __ardour_gtk_bbt_marker_dialog_h__
+#pragma once
 
 #include <gtkmm/box.h>
 #include <gtkmm/entry.h>
@@ -57,4 +56,3 @@ private:
 	Gtk::Label      name_label;
 };
 
-#endif /* __ardour_gtk_bbt_marker_dialog_h__ */
diff --git a/gtk2_ardour/big_clock_window.h b/gtk2_ardour/big_clock_window.h
index 766be1c5be..12ecb67b4a 100644
--- a/gtk2_ardour/big_clock_window.h
+++ b/gtk2_ardour/big_clock_window.h
@@ -17,8 +17,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __bigclock_window_h__
-#define __bigclock_window_h__
+#pragma once
 
 #include "ardour_window.h"
 
@@ -39,5 +38,4 @@ private:
 	bool on_key_press_event (GdkEventKey*);
 };
 
-#endif // __ardour_window_h__
 
diff --git a/gtk2_ardour/bundle_manager.h b/gtk2_ardour/bundle_manager.h
index 9f0f84d2f9..33b9dfdccd 100644
--- a/gtk2_ardour/bundle_manager.h
+++ b/gtk2_ardour/bundle_manager.h
@@ -18,8 +18,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_ui_bundle_manager_h__
-#define __ardour_ui_bundle_manager_h__
+#pragma once
 
 #include <gtkmm/entry.h>
 #include <gtkmm/liststore.h>
@@ -137,4 +136,3 @@ private:
 	bool _adding;
 };
 
-#endif
diff --git a/gtk2_ardour/clock_group.h b/gtk2_ardour/clock_group.h
index 182db2ff7d..31aae14d51 100644
--- a/gtk2_ardour/clock_group.h
+++ b/gtk2_ardour/clock_group.h
@@ -17,8 +17,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_clock_group_h__
-#define __gtk_ardour_clock_group_h__
+#pragma once
 
 #include <set>
 #include <sigc++/signal.h>
@@ -45,4 +44,3 @@ private:
 	void one_clock_changed (AudioClock*);
 };
 
-#endif /* __gtk_ardour_clock_group_h__ */
diff --git a/gtk2_ardour/color_theme_manager.h b/gtk2_ardour/color_theme_manager.h
index d1b98e19a8..18c9ccbf8e 100644
--- a/gtk2_ardour/color_theme_manager.h
+++ b/gtk2_ardour/color_theme_manager.h
@@ -17,8 +17,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_gtk_color_manager_h__
-#define __ardour_gtk_color_manager_h__
+#pragma once
 
 #include <gtkmm/treeview.h>
 #include <gtkmm/treestore.h>
@@ -164,4 +163,3 @@ private:
 
 };
 
-#endif /* __ardour_gtk_color_manager_h__ */
diff --git a/gtk2_ardour/control_point.h b/gtk2_ardour/control_point.h
index fa6f7920de..0a13ecdcd5 100644
--- a/gtk2_ardour/control_point.h
+++ b/gtk2_ardour/control_point.h
@@ -19,8 +19,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_control_point_h__
-#define __ardour_control_point_h__
+#pragma once
 
 #include <sys/types.h>
 #include <gdk/gdkevents.h>
@@ -104,5 +103,4 @@ private:
 };
 
 
-#endif /* __ardour_control_point_h__ */
 
diff --git a/gtk2_ardour/crossfade_edit.h b/gtk2_ardour/crossfade_edit.h
index a90cbe91ef..dea7c37642 100644
--- a/gtk2_ardour/crossfade_edit.h
+++ b/gtk2_ardour/crossfade_edit.h
@@ -21,8 +21,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_xfade_edit_h__
-#define __gtk_ardour_xfade_edit_h__
+#pragma once
 
 #include <list>
 
@@ -232,4 +231,3 @@ private:
 	void dump ();
 };
 
-#endif /* __gtk_ardour_xfade_edit_h__ */
diff --git a/gtk2_ardour/crossfade_view.h b/gtk2_ardour/crossfade_view.h
index f953601615..60c3d0a5a6 100644
--- a/gtk2_ardour/crossfade_view.h
+++ b/gtk2_ardour/crossfade_view.h
@@ -20,8 +20,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_crossfade_view_h__
-#define __gtk_ardour_crossfade_view_h__
+#pragma once
 
 #include <vector>
 #include "pbd/signals.h"
@@ -86,4 +85,3 @@ private:
 	void color_handler ();
 };
 
-#endif /* __gtk_ardour_crossfade_view_h__ */
diff --git a/gtk2_ardour/cue_editor.h b/gtk2_ardour/cue_editor.h
index 8e922a3fa6..1c794fc652 100644
--- a/gtk2_ardour/cue_editor.h
+++ b/gtk2_ardour/cue_editor.h
@@ -16,8 +16,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_cue_editor_h__
-#define __gtk_ardour_cue_editor_h__
+#pragma once
 
 #include "pbd/history_owner.h"
 
@@ -114,4 +113,3 @@ class CueEditor : public EditingContext, public PBD::HistoryOwner, public sigc::
 	void do_redo (uint32_t n);
 };
 
-#endif /* __gtk_ardour_cue_editor_h__ */
diff --git a/gtk2_ardour/cursor_context.h b/gtk2_ardour/cursor_context.h
index 361176e1e2..b9453b2140 100644
--- a/gtk2_ardour/cursor_context.h
+++ b/gtk2_ardour/cursor_context.h
@@ -16,8 +16,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_gtk_cursor_context_h__
-#define __ardour_gtk_cursor_context_h__
+#pragma once
 
 #include <memory>
 
@@ -72,4 +71,3 @@ private:
 	CursorContext(EditingContext&, Gdk::Cursor* cursor);
 };
 
-#endif /* __ardour_gtk_cursor_context_h__ */
diff --git a/gtk2_ardour/dsp_stats_window.h b/gtk2_ardour/dsp_stats_window.h
index a94bcc503c..bf53912db3 100644
--- a/gtk2_ardour/dsp_stats_window.h
+++ b/gtk2_ardour/dsp_stats_window.h
@@ -16,8 +16,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_dspstats_window_h__
-#define __ardour_dspstats_window_h__
+#pragma once
 
 
 #include "ardour_window.h"
@@ -41,5 +40,4 @@ private:
 	DspStatisticsGUI* ui;
 };
 
-#endif
 
diff --git a/gtk2_ardour/duplicate_routes_dialog.h b/gtk2_ardour/duplicate_routes_dialog.h
index 452103b06f..6049e72cac 100644
--- a/gtk2_ardour/duplicate_routes_dialog.h
+++ b/gtk2_ardour/duplicate_routes_dialog.h
@@ -16,8 +16,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_duplicate_route_dialog_h__
-#define __gtk_ardour_duplicate_route_dialog_h__
+#pragma once
 
 #include <gtkmm/entry.h>
 #include <gtkmm/box.h>
@@ -67,4 +66,3 @@ private:
 	Gtk::ComboBoxText insert_at_combo;
 };
 
-#endif /* __gtk_ardour_duplicate_route_dialog_h__ */
diff --git a/gtk2_ardour/editing.h b/gtk2_ardour/editing.h
index 304eb3af7f..000768d9d9 100644
--- a/gtk2_ardour/editing.h
+++ b/gtk2_ardour/editing.h
@@ -18,8 +18,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_editing_h__
-#define __gtk_ardour_editing_h__
+#pragma once
 
 #include <string>
 #include <map>
@@ -261,4 +260,3 @@ enum RegionActionTarget {
 
 } // namespace Editing
 
-#endif // __gtk_ardour_editing_h__
diff --git a/gtk2_ardour/editing_context.h b/gtk2_ardour/editing_context.h
index d71917404d..6fd1121074 100644
--- a/gtk2_ardour/editing_context.h
+++ b/gtk2_ardour/editing_context.h
@@ -30,8 +30,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_midi_editing_context_h__
-#define __ardour_midi_editing_context_h__
+#pragma once
 
 #include "pbd/signals.h"
 
@@ -709,4 +708,3 @@ class EditingContext : public ARDOUR::SessionHandlePtr, public AxisViewProvider
 };
 
 
-#endif /* __ardour_midi_editing_context_h__ */
diff --git a/gtk2_ardour/editor.h b/gtk2_ardour/editor.h
index 697853eb22..37a92500eb 100644
--- a/gtk2_ardour/editor.h
+++ b/gtk2_ardour/editor.h
@@ -31,8 +31,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_editor_h__
-#define __ardour_editor_h__
+#pragma once
 
 #include <sys/time.h>
 
@@ -2338,4 +2337,3 @@ private:
 	friend class RhythmFerret;
 };
 
-#endif /* __ardour_editor_h__ */
diff --git a/gtk2_ardour/editor_automation_line.h b/gtk2_ardour/editor_automation_line.h
index ad384aa4e7..4363cb8e7e 100644
--- a/gtk2_ardour/editor_automation_line.h
+++ b/gtk2_ardour/editor_automation_line.h
@@ -23,8 +23,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_automation_line_h__
-#define __ardour_automation_line_h__
+#pragma once
 
 #include <vector>
 #include <list>
@@ -79,5 +78,4 @@ public:
 	virtual bool event_handler (GdkEvent*);
 };
 
-#endif /* __ardour_automation_line_h__ */
 
diff --git a/gtk2_ardour/editor_component.h b/gtk2_ardour/editor_component.h
index 4698e37f1d..19e262fa65 100644
--- a/gtk2_ardour/editor_component.h
+++ b/gtk2_ardour/editor_component.h
@@ -16,8 +16,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_gtk_editor_component_h__
-#define __ardour_gtk_editor_component_h__
+#pragma once
 
 class Editor;
 
@@ -31,4 +30,3 @@ protected:
 	Editor* _editor;
 };
 
-#endif
diff --git a/gtk2_ardour/editor_cursors.h b/gtk2_ardour/editor_cursors.h
index 4344ee54a4..6fd8831a76 100644
--- a/gtk2_ardour/editor_cursors.h
+++ b/gtk2_ardour/editor_cursors.h
@@ -19,8 +19,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_editor_cursors_h__
-#define __gtk_ardour_editor_cursors_h__
+#pragma once
 
 #include "pbd/signals.h"
 #include "ardour/types.h"
@@ -62,4 +61,3 @@ private:
 	samplepos_t           _current_sample;
 };
 
-#endif // __gtk_ardour_editor_cursors_h__
diff --git a/gtk2_ardour/editor_group_tabs.h b/gtk2_ardour/editor_group_tabs.h
index f2eb5ca7be..e40e844ccb 100644
--- a/gtk2_ardour/editor_group_tabs.h
+++ b/gtk2_ardour/editor_group_tabs.h
@@ -17,8 +17,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_editor_group_tabs_h__
-#define __gtk_ardour_editor_group_tabs_h__
+#pragma once
 
 #include <gtkmm/menu.h>
 #include "group_tabs.h"
@@ -43,4 +42,3 @@ private:
 	}
 };
 
-#endif // __gtk_ardour_editor_group_tabs_h__
diff --git a/gtk2_ardour/editor_locations.h b/gtk2_ardour/editor_locations.h
index 2f8ee1af92..ea7fcd0a1d 100644
--- a/gtk2_ardour/editor_locations.h
+++ b/gtk2_ardour/editor_locations.h
@@ -18,8 +18,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_editor_locations_h__
-#define __gtk_ardour_editor_locations_h__
+#pragma once
 
 #include "pbd/xml++.h"
 
@@ -50,4 +49,3 @@ private:
 };
 
 
-#endif /* __gtk_ardour_editor_locations_h__ */
diff --git a/gtk2_ardour/editor_regions.h b/gtk2_ardour/editor_regions.h
index d707d5dea9..0253ad1be8 100644
--- a/gtk2_ardour/editor_regions.h
+++ b/gtk2_ardour/editor_regions.h
@@ -19,8 +19,7 @@
  * with this program; if not, write to the Free Software Foundation, Inc.,
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
-#ifndef __gtk_ardour_editor_regions_h__
-#define __gtk_ardour_editor_regions_h__
+#pragma once
 
 #include "editor_component.h"
 #include "region_list_base.h"
@@ -52,4 +51,3 @@ private:
 	void show_context_menu (int button, int time);
 };
 
-#endif /* __gtk_ardour_editor_regions_h__ */
diff --git a/gtk2_ardour/editor_route_groups.h b/gtk2_ardour/editor_route_groups.h
index 4b9cde9e1e..b99f7ce178 100644
--- a/gtk2_ardour/editor_route_groups.h
+++ b/gtk2_ardour/editor_route_groups.h
@@ -18,8 +18,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_editor_route_groups_h__
-#define __gtk_ardour_editor_route_groups_h__
+#pragma once
 
 #include <gtkmm/liststore.h>
 #include <gtkmm/scrolledwindow.h>
@@ -101,4 +100,3 @@ private:
 	Gtk::ColorSelectionDialog color_dialog;
 };
 
-#endif // __gtk_ardour_editor_route_groups_h__
diff --git a/gtk2_ardour/editor_section_box.h b/gtk2_ardour/editor_section_box.h
index f993e0ab59..55dccce99d 100644
--- a/gtk2_ardour/editor_section_box.h
+++ b/gtk2_ardour/editor_section_box.h
@@ -17,8 +17,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_section_box_h__
-#define __gtk_ardour_section_box_h__
+#pragma once
 
 #include "ardour/types.h"
 
@@ -38,4 +37,3 @@ private:
 	Editor& _editor;
 };
 
-#endif // __gtk_ardour_editor_cursors_h__
diff --git a/gtk2_ardour/editor_snapshots.h b/gtk2_ardour/editor_snapshots.h
index 2f9bb5bedc..4b29e1b83a 100644
--- a/gtk2_ardour/editor_snapshots.h
+++ b/gtk2_ardour/editor_snapshots.h
@@ -18,8 +18,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_editor_snapshots_h__
-#define __gtk_ardour_editor_snapshots_h__
+#pragma once
 
 #include "ardour/session_handle.h"
 
@@ -69,4 +68,3 @@ private:
 	void rename (std::string);
 };
 
-#endif // __gtk_ardour_editor_snapshots_h__
diff --git a/gtk2_ardour/editor_sources.h b/gtk2_ardour/editor_sources.h
index 0ee9ed2f77..272d246d7f 100644
--- a/gtk2_ardour/editor_sources.h
+++ b/gtk2_ardour/editor_sources.h
@@ -15,8 +15,7 @@
  * with this program; if not, write to the Free Software Foundation, Inc.,
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
-#ifndef __gtk_ardour_editor_sources_h__
-#define __gtk_ardour_editor_sources_h__
+#pragma once
 
 #include "editor_component.h"
 #include "source_list_base.h"
@@ -43,4 +42,3 @@ private:
 	void drag_data_received (Glib::RefPtr<Gdk::DragContext> const&, gint, gint, Gtk::SelectionData const&, guint, guint);
 };
 
-#endif
diff --git a/gtk2_ardour/editor_summary.h b/gtk2_ardour/editor_summary.h
index 4ae38a9e82..5de5189b3b 100644
--- a/gtk2_ardour/editor_summary.h
+++ b/gtk2_ardour/editor_summary.h
@@ -19,8 +19,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_editor_summary_h__
-#define __gtk_ardour_editor_summary_h__
+#pragma once
 
 #include "gtkmm2ext/cairo_widget.h"
 #include "editor_component.h"
@@ -137,4 +136,3 @@ private:
 	PBD::ScopedConnectionList region_property_connection;
 };
 
-#endif
diff --git a/gtk2_ardour/enums.h b/gtk2_ardour/enums.h
index 5f92746cfa..866297f0a2 100644
--- a/gtk2_ardour/enums.h
+++ b/gtk2_ardour/enums.h
@@ -19,8 +19,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_gtk_enums_h__
-#define __ardour_gtk_enums_h__
+#pragma once
 
 #include "ardour/types.h"
 
@@ -56,4 +55,3 @@ enum Height {
 
 extern void setup_gtk_ardour_enums ();
 
-#endif /* __ardour_gtk_enums_h__ */
diff --git a/gtk2_ardour/export_channel_selector.h b/gtk2_ardour/export_channel_selector.h
index 5897a12f98..cdd829847b 100644
--- a/gtk2_ardour/export_channel_selector.h
+++ b/gtk2_ardour/export_channel_selector.h
@@ -20,8 +20,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __export_channel_selector_h__
-#define __export_channel_selector_h__
+#pragma once
 
 #include <list>
 #include <memory>
@@ -298,4 +297,3 @@ class TrackExportChannelSelector : public ExportChannelSelector
 	bool _syncing_with_manager;
 };
 
-#endif /* __export_channel_selector_h__ */
diff --git a/gtk2_ardour/export_dialog.h b/gtk2_ardour/export_dialog.h
index d54f3d8c77..ae2006c50e 100644
--- a/gtk2_ardour/export_dialog.h
+++ b/gtk2_ardour/export_dialog.h
@@ -22,8 +22,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __export_dialog_h__
-#define __export_dialog_h__
+#pragma once
 
 #include <string>
 #include <boost/scoped_ptr.hpp>
@@ -207,4 +206,3 @@ class StemExportDialog : public ExportDialog
 	void init_components ();
 };
 
-#endif /* __ardour_export_dialog_h__ */
diff --git a/gtk2_ardour/export_file_notebook.h b/gtk2_ardour/export_file_notebook.h
index e8b2f462f6..5c17c11ca6 100644
--- a/gtk2_ardour/export_file_notebook.h
+++ b/gtk2_ardour/export_file_notebook.h
@@ -21,8 +21,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __export_file_notebook_h__
-#define __export_file_notebook_h__
+#pragma once
 
 #include <sigc++/signal.h>
 
@@ -143,4 +142,3 @@ private:
 	};
 };
 
-#endif
diff --git a/gtk2_ardour/export_filename_selector.h b/gtk2_ardour/export_filename_selector.h
index 553cd5f19f..d14c4b7059 100644
--- a/gtk2_ardour/export_filename_selector.h
+++ b/gtk2_ardour/export_filename_selector.h
@@ -18,8 +18,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __export_filename_selector_h__
-#define __export_filename_selector_h__
+#pragma once
 
 #include <gtkmm/box.h>
 #include <gtkmm/button.h>
@@ -139,4 +138,3 @@ private:
 	bool _require_timespan;
 };
 
-#endif /* __export_filename_selector_h__ */
diff --git a/gtk2_ardour/export_format_dialog.h b/gtk2_ardour/export_format_dialog.h
index 4803410148..031f2fba7a 100644
--- a/gtk2_ardour/export_format_dialog.h
+++ b/gtk2_ardour/export_format_dialog.h
@@ -20,8 +20,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __export_format_dialog_h__
-#define __export_format_dialog_h__
+#pragma once
 
 #include "ardour/types.h"
 #include "ardour/export_format_manager.h"
@@ -412,4 +411,3 @@ private:
 
 };
 
-#endif /* __export_format_dialog_h__ */
diff --git a/gtk2_ardour/export_format_selector.h b/gtk2_ardour/export_format_selector.h
index 92b0cf71e3..842d746a60 100644
--- a/gtk2_ardour/export_format_selector.h
+++ b/gtk2_ardour/export_format_selector.h
@@ -18,8 +18,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __export_format_selector_h__
-#define __export_format_selector_h__
+#pragma once
 
 #include <memory>
 #include <string>
@@ -94,4 +93,3 @@ private:
 	Gtk::Button new_button;
 };
 
-#endif /* __export_format_selector_h__ */
diff --git a/gtk2_ardour/export_preset_selector.h b/gtk2_ardour/export_preset_selector.h
index e8688026cf..ce78d13c02 100644
--- a/gtk2_ardour/export_preset_selector.h
+++ b/gtk2_ardour/export_preset_selector.h
@@ -18,8 +18,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __export_preset_selector_h__
-#define __export_preset_selector_h__
+#pragma once
 
 #include <sigc++/signal.h>
 
@@ -84,4 +83,3 @@ private:
 	sigc::connection select_connection;
 };
 
-#endif
diff --git a/gtk2_ardour/export_timespan_selector.h b/gtk2_ardour/export_timespan_selector.h
index e5b65ee79c..41ab6cdee2 100644
--- a/gtk2_ardour/export_timespan_selector.h
+++ b/gtk2_ardour/export_timespan_selector.h
@@ -21,8 +21,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __export_timespan_selector_h__
-#define __export_timespan_selector_h__
+#pragma once
 
 #include <ctime>
 #include <list>
@@ -198,4 +197,3 @@ private:
 	std::string range_id;
 };
 
-#endif /* __export_timespan_selector_h__ */
diff --git a/gtk2_ardour/export_video_dialog.h b/gtk2_ardour/export_video_dialog.h
index dc990403ba..9e7c988117 100644
--- a/gtk2_ardour/export_video_dialog.h
+++ b/gtk2_ardour/export_video_dialog.h
@@ -15,8 +15,7 @@
  * with this program; if not, write to the Free Software Foundation, Inc.,
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
-#ifndef __gtk_ardour_export_video_dialog_h__
-#define __gtk_ardour_export_video_dialog_h__
+#pragma once
 
 #include <string>
 
@@ -108,4 +107,3 @@ private:
 	Gtk::CheckButton debug_checkbox;
 };
 
-#endif /* __gtk_ardour_export_video_dialog_h__ */
diff --git a/gtk2_ardour/fft.h b/gtk2_ardour/fft.h
index b0003a7c4e..0ed7316437 100644
--- a/gtk2_ardour/fft.h
+++ b/gtk2_ardour/fft.h
@@ -16,8 +16,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_fft_h__
-#define __ardour_fft_h__
+#pragma once
 
 
 #include <iostream>
@@ -72,4 +71,3 @@ private:
 
 }
 
-#endif
diff --git a/gtk2_ardour/floating_text_entry.h b/gtk2_ardour/floating_text_entry.h
index 23db9707cf..6d943624cf 100644
--- a/gtk2_ardour/floating_text_entry.h
+++ b/gtk2_ardour/floating_text_entry.h
@@ -17,8 +17,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __floating_text_entry_h__
-#define __floating_text_entry_h__
+#pragma once
 
 #include <gtkmm/entry.h>
 #include <gtkmm/window.h>
@@ -58,4 +57,3 @@ private:
 	void on_hide ();
 };
 
-#endif // __ardour_window_h__
diff --git a/gtk2_ardour/gain_meter.h b/gtk2_ardour/gain_meter.h
index b012925140..bb24236784 100644
--- a/gtk2_ardour/gain_meter.h
+++ b/gtk2_ardour/gain_meter.h
@@ -23,8 +23,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_gtk_gain_meter_h__
-#define __ardour_gtk_gain_meter_h__
+#pragma once
 
 #include <vector>
 #include <map>
@@ -264,5 +263,4 @@ class GainMeter : public GainMeterBase, public Gtk::VBox
 	std::vector<ARDOUR::DataType> _types;
 };
 
-#endif /* __ardour_gtk_gain_meter_h__ */
 
diff --git a/gtk2_ardour/ghostregion.h b/gtk2_ardour/ghostregion.h
index fbeeb800c0..417e9c1970 100644
--- a/gtk2_ardour/ghostregion.h
+++ b/gtk2_ardour/ghostregion.h
@@ -22,8 +22,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_gtk_ghost_region_h__
-#define __ardour_gtk_ghost_region_h__
+#pragma once
 
 #include <vector>
 
@@ -137,4 +136,3 @@ public:
 	GhostEvent::EventList::iterator _optimization_iterator;
 };
 
-#endif /* __ardour_gtk_ghost_region_h__ */
diff --git a/gtk2_ardour/global_port_matrix.h b/gtk2_ardour/global_port_matrix.h
index 3381563572..27dca45de3 100644
--- a/gtk2_ardour/global_port_matrix.h
+++ b/gtk2_ardour/global_port_matrix.h
@@ -18,8 +18,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_gtk_global_port_matrix_h__
-#define __ardour_gtk_global_port_matrix_h__
+#pragma once
 
 #include <gtkmm/button.h>
 #include "port_matrix.h"
@@ -68,4 +67,3 @@ private:
 };
 
 
-#endif
diff --git a/gtk2_ardour/grid_lines.h b/gtk2_ardour/grid_lines.h
index 216e171e35..62de80a9ad 100644
--- a/gtk2_ardour/grid_lines.h
+++ b/gtk2_ardour/grid_lines.h
@@ -16,8 +16,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_grid_lines_h__
-#define __ardour_grid_lines_h__
+#pragma once
 
 #include "canvas/line_set.h"
 #include "canvas/ruler.h"
@@ -38,4 +37,3 @@ private:
 	ArdourCanvas::LineSet lines;
 };
 
-#endif /* __ardour_grid_lines_h__ */
diff --git a/gtk2_ardour/group_tabs.h b/gtk2_ardour/group_tabs.h
index 2b29b421c1..41829f7d6a 100644
--- a/gtk2_ardour/group_tabs.h
+++ b/gtk2_ardour/group_tabs.h
@@ -19,8 +19,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_group_tabs_h__
-#define __gtk_ardour_group_tabs_h__
+#pragma once
 
 #include <gtkmm/menu.h>
 
@@ -184,4 +183,3 @@ private:
 	static std::list<Gdk::Color> _used_colors;
 };
 
-#endif // __gtk_ardour_group_tabs_h__
diff --git a/gtk2_ardour/gui_object.h b/gtk2_ardour/gui_object.h
index f80e19ae8f..11c3b46d64 100644
--- a/gtk2_ardour/gui_object.h
+++ b/gtk2_ardour/gui_object.h
@@ -18,8 +18,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_gui_object_h__
-#define __gtk_ardour_gui_object_h__
+#pragma once
 
 #include <map>
 #include <string>
@@ -74,4 +73,3 @@ public:
 	std::map <std::string, XMLNode*> object_map;
 };
 
-#endif /* __gtk_ardour_gui_object_h__ */
diff --git a/gtk2_ardour/hit.h b/gtk2_ardour/hit.h
index c9f83e9d87..160429848f 100644
--- a/gtk2_ardour/hit.h
+++ b/gtk2_ardour/hit.h
@@ -17,8 +17,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_hit_h__
-#define __gtk_ardour_hit_h__
+#pragma once
 
 #include <iostream>
 #include "note_base.h"
@@ -72,4 +71,3 @@ private:
 	ArdourCanvas::Polygon* _polygon;
 };
 
-#endif /* __gtk_ardour_hit_h__ */
diff --git a/gtk2_ardour/idleometer.h b/gtk2_ardour/idleometer.h
index d21250fc1a..589077f7b7 100644
--- a/gtk2_ardour/idleometer.h
+++ b/gtk2_ardour/idleometer.h
@@ -16,8 +16,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_idle_o_meter_h__
-#define __ardour_idle_o_meter_h__
+#pragma once
 
 #include <gtkmm/label.h>
 #include "ardour_dialog.h"
@@ -55,5 +54,4 @@ private:
 	double _var_m, _var_s;
 	sigc::connection _idle_connection;
 };
-#endif
 
diff --git a/gtk2_ardour/input_port_monitor.h b/gtk2_ardour/input_port_monitor.h
index b1fa0cbab9..ecca0b0ef0 100644
--- a/gtk2_ardour/input_port_monitor.h
+++ b/gtk2_ardour/input_port_monitor.h
@@ -16,8 +16,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_input_port_monitor_h__
-#define __gtk_ardour_input_port_monitor_h__
+#pragma once
 
 #include <gtkmm/box.h>
 #include <gtkmm/alignment.h>
@@ -134,4 +133,3 @@ private:
 	Orientation               _orientation;
 };
 
-#endif
diff --git a/gtk2_ardour/instrument_selector.h b/gtk2_ardour/instrument_selector.h
index 687b40b681..dc08c869ee 100644
--- a/gtk2_ardour/instrument_selector.h
+++ b/gtk2_ardour/instrument_selector.h
@@ -16,8 +16,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_instrument_selector_h__
-#define __gtk_ardour_instrument_selector_h__
+#pragma once
 
 #include <string>
 
@@ -76,4 +75,3 @@ private:
 	PBD::ScopedConnection        _update_connection;
 };
 
-#endif /* __gtk_ardour_instrument_selector_h__ */
diff --git a/gtk2_ardour/interthread_progress_window.h b/gtk2_ardour/interthread_progress_window.h
index beb31c0be9..ef71bc0863 100644
--- a/gtk2_ardour/interthread_progress_window.h
+++ b/gtk2_ardour/interthread_progress_window.h
@@ -18,8 +18,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_interthread_progress_window_h__
-#define __ardour_interthread_progress_window_h__
+#pragma once
 
 #include <gtkmm/label.h>
 #include <gtkmm/progressbar.h>
@@ -68,4 +67,3 @@ private:
 	ARDOUR::ImportStatus* _import_status;
 };
 
-#endif
diff --git a/gtk2_ardour/io_selector.h b/gtk2_ardour/io_selector.h
index 8468790e79..bc12685ccb 100644
--- a/gtk2_ardour/io_selector.h
+++ b/gtk2_ardour/io_selector.h
@@ -20,8 +20,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtkardour_io_selector_h__
-#define __gtkardour_io_selector_h__
+#pragma once
 
 #include "port_matrix.h"
 #include "ardour_window.h"
@@ -88,4 +87,3 @@ class IOSelectorWindow : public ArdourWindow
 	bool wm_delete (GdkEventAny*);
 };
 
-#endif /* __gtkardour_io_selector_h__ */
diff --git a/gtk2_ardour/item_counts.h b/gtk2_ardour/item_counts.h
index 94bedd04e7..9e129a5bca 100644
--- a/gtk2_ardour/item_counts.h
+++ b/gtk2_ardour/item_counts.h
@@ -16,8 +16,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_item_counts_h__
-#define __ardour_item_counts_h__
+#pragma once
 
 #include <cstddef>
 #include <map>
@@ -80,4 +79,3 @@ private:
 	size_t                              _notes;
 };
 
-#endif /* __ardour_item_counts_h__ */
diff --git a/gtk2_ardour/keyboard.h b/gtk2_ardour/keyboard.h
index 8b5d6ac0fb..74ec69b57a 100644
--- a/gtk2_ardour/keyboard.h
+++ b/gtk2_ardour/keyboard.h
@@ -20,8 +20,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_keyboard_h__
-#define __ardour_keyboard_h__
+#pragma once
 
 #include <map>
 #include <string>
@@ -108,4 +107,3 @@ private:
 	void find_bindings_files (std::map<std::string,std::string>& files);
 };
 
-#endif /* __ardour_keyboard_h__ */
diff --git a/gtk2_ardour/keyeditor.h b/gtk2_ardour/keyeditor.h
index 91adadbe74..cc4c32a9b3 100644
--- a/gtk2_ardour/keyeditor.h
+++ b/gtk2_ardour/keyeditor.h
@@ -18,8 +18,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_gtk_key_editor_h__
-#define __ardour_gtk_key_editor_h__
+#pragma once
 
 #include <string>
 
@@ -136,4 +135,3 @@ private:
 	sigc::connection _refresh_connection;
 };
 
-#endif /* __ardour_gtk_key_editor_h__ */
diff --git a/gtk2_ardour/level_meter.h b/gtk2_ardour/level_meter.h
index 760a47b7ce..2cdc1db642 100644
--- a/gtk2_ardour/level_meter.h
+++ b/gtk2_ardour/level_meter.h
@@ -19,8 +19,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_gtk_track_meter_h__
-#define __ardour_gtk_track_meter_h__
+#pragma once
 
 #include <vector>
 
@@ -145,5 +144,4 @@ protected:
 	void mtr_remove(Gtk::Widget &w);
 };
 
-#endif /* __ardour_gtk_track_meter_h__ */
 
diff --git a/gtk2_ardour/location_ui.h b/gtk2_ardour/location_ui.h
index b04e7af890..31a2759f40 100644
--- a/gtk2_ardour/location_ui.h
+++ b/gtk2_ardour/location_ui.h
@@ -20,8 +20,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_location_ui_h__
-#define __ardour_location_ui_h__
+#pragma once
 
 #include <gtkmm/box.h>
 #include <gtkmm/checkbutton.h>
@@ -239,4 +238,3 @@ protected:
 	void session_going_away();
 };
 
-#endif // __ardour_location_ui_h__
diff --git a/gtk2_ardour/luainstance.h b/gtk2_ardour/luainstance.h
index 15d9fb0590..0e10740603 100644
--- a/gtk2_ardour/luainstance.h
+++ b/gtk2_ardour/luainstance.h
@@ -16,8 +16,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtkardour_luainstance_h__
-#define __gtkardour_luainstance_h__
+#pragma once
 
 #include <bitset>
 
@@ -191,4 +190,3 @@ private:
 
 };
 
-#endif
diff --git a/gtk2_ardour/luawindow.h b/gtk2_ardour/luawindow.h
index d049cc77be..2f9be48f7c 100644
--- a/gtk2_ardour/luawindow.h
+++ b/gtk2_ardour/luawindow.h
@@ -15,8 +15,7 @@
  * with this program; if not, write to the Free Software Foundation, Inc.,
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
-#ifndef __ardour_luawindow_h__
-#define __ardour_luawindow_h__
+#pragma once
 
 #include <glibmm/thread.h>
 
@@ -140,4 +139,3 @@ private:
 };
 
 
-#endif
diff --git a/gtk2_ardour/lxvst_plugin_ui.h b/gtk2_ardour/lxvst_plugin_ui.h
index eb68591665..c5b9ba3587 100644
--- a/gtk2_ardour/lxvst_plugin_ui.h
+++ b/gtk2_ardour/lxvst_plugin_ui.h
@@ -17,8 +17,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __lxvst_plugin_ui_h__
-#define __lxvst_plugin_ui_h__
+#pragma once
 
 #include "pbd/signals.h"
 #include "vst_plugin_ui.h"
@@ -54,4 +53,3 @@ private:
 
 #endif //LXVST_SUPPORT
 
-#endif
diff --git a/gtk2_ardour/main_clock.h b/gtk2_ardour/main_clock.h
index 9050f83128..3b4ca44715 100644
--- a/gtk2_ardour/main_clock.h
+++ b/gtk2_ardour/main_clock.h
@@ -17,8 +17,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_main_clock_h__
-#define __gtk_ardour_main_clock_h__
+#pragma once
 
 #include "audio_clock.h"
 
@@ -46,4 +45,3 @@ private:
 	ARDOUR::ClockDeltaMode _delta_mode;
 };
 
-#endif // __gtk_ardour_main_clock_h__
diff --git a/gtk2_ardour/marker.h b/gtk2_ardour/marker.h
index c29736333c..0c2bb0a39f 100644
--- a/gtk2_ardour/marker.h
+++ b/gtk2_ardour/marker.h
@@ -21,8 +21,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_marker_h__
-#define __gtk_ardour_marker_h__
+#pragma once
 
 #include <string>
 #include <glib.h>
@@ -248,4 +247,3 @@ class BBTMarker : public MetricMarker
 	MeterMarker* meter_marker;
 };
 
-#endif /* __gtk_ardour_marker_h__ */
diff --git a/gtk2_ardour/marker_selection.h b/gtk2_ardour/marker_selection.h
index ed65e03095..83c7aad015 100644
--- a/gtk2_ardour/marker_selection.h
+++ b/gtk2_ardour/marker_selection.h
@@ -17,8 +17,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_gtk_marker_selection_h__
-#define __ardour_gtk_marker_selection_h__
+#pragma once
 
 #include <list>
 
@@ -30,4 +29,3 @@ class MarkerSelection : public std::list<ArdourMarker*>
 	void range (Temporal::timepos_t& start, Temporal::timepos_t& end);
 };
 
-#endif /* __ardour_gtk_marker_selection_h__ */
diff --git a/gtk2_ardour/meterbridge.h b/gtk2_ardour/meterbridge.h
index 8f381cd502..d759919550 100644
--- a/gtk2_ardour/meterbridge.h
+++ b/gtk2_ardour/meterbridge.h
@@ -16,8 +16,7 @@
  * with this program; if not, write to the Free Software Foundation, Inc.,
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
-#ifndef __ardour_meterbridge_h__
-#define __ardour_meterbridge_h__
+#pragma once
 
 #include <glibmm/thread.h>
 
@@ -156,4 +155,3 @@ private:
 	bool on_configure_event (GdkEventConfigure* conf);
 };
 
-#endif
diff --git a/gtk2_ardour/midi_channel_selector.h b/gtk2_ardour/midi_channel_selector.h
index 7ed6a7f718..1e0e44558e 100644
--- a/gtk2_ardour/midi_channel_selector.h
+++ b/gtk2_ardour/midi_channel_selector.h
@@ -20,8 +20,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_ui_midi_channel_selector_h__
-#define __ardour_ui_midi_channel_selector_h__
+#pragma once
 
 #include <set>
 #include "sigc++/trackable.h"
@@ -182,4 +181,3 @@ private:
 	void playback_mode_toggled (ARDOUR::ChannelMode);
 };
 
-#endif /*__ardour_ui_midi_channel_selector_h__*/
diff --git a/gtk2_ardour/midi_clip_editor.h b/gtk2_ardour/midi_clip_editor.h
index 65ac4d94ee..8a9800e369 100644
--- a/gtk2_ardour/midi_clip_editor.h
+++ b/gtk2_ardour/midi_clip_editor.h
@@ -17,8 +17,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __midi_region_trimmer_box_h__
-#define __midi_region_trimmer_box_h__
+#pragma once
 
 #include <map>
 
@@ -74,4 +73,3 @@ private:
 	std::shared_ptr<ARDOUR::Region> _region;
 };
 
-#endif /* __midi_region_trimmer_box_h__ */
diff --git a/gtk2_ardour/midi_cue_editor.h b/gtk2_ardour/midi_cue_editor.h
index 1d5e6a536b..52a76062b4 100644
--- a/gtk2_ardour/midi_cue_editor.h
+++ b/gtk2_ardour/midi_cue_editor.h
@@ -16,8 +16,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_midi_cue_editor_h__
-#define __gtk_ardour_midi_cue_editor_h__
+#pragma once
 
 #include <gtkmm/adjustment.h>
 
@@ -205,4 +204,3 @@ class MidiCueEditor : public CueEditor
 };
 
 
-#endif /* __gtk_ardour_midi_cue_editor_h__ */
diff --git a/gtk2_ardour/midi_cue_view.h b/gtk2_ardour/midi_cue_view.h
index e949d84036..ff15e5ce0a 100644
--- a/gtk2_ardour/midi_cue_view.h
+++ b/gtk2_ardour/midi_cue_view.h
@@ -22,8 +22,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_midi_cue_view_h__
-#define __gtk_ardour_midi_cue_view_h__
+#pragma once
 
 #include "midi_view.h"
 
@@ -76,4 +75,3 @@ class MidiCueView : public MidiView
 };
 
 
-#endif /* __gtk_ardour_midi_cue_view_h__ */
diff --git a/gtk2_ardour/midi_cut_buffer.h b/gtk2_ardour/midi_cut_buffer.h
index 47e733f340..558aae6d99 100644
--- a/gtk2_ardour/midi_cut_buffer.h
+++ b/gtk2_ardour/midi_cut_buffer.h
@@ -17,8 +17,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_midi_cut_buffer_h__
-#define __gtk_ardour_midi_cut_buffer_h__
+#pragma once
 
 #include "temporal/beats.h"
 
@@ -45,4 +44,3 @@ private:
 	TimeType _origin;
 };
 
-#endif /* __gtk_ardour_midi_cut_buffer_h__ */
diff --git a/gtk2_ardour/midi_region_operations_box.h b/gtk2_ardour/midi_region_operations_box.h
index 67ddf93eee..4e937eb56e 100644
--- a/gtk2_ardour/midi_region_operations_box.h
+++ b/gtk2_ardour/midi_region_operations_box.h
@@ -17,8 +17,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __midi_region_operations_box_h__
-#define __midi_region_operations_box_h__
+#pragma once
 
 #include <map>
 
@@ -63,4 +62,3 @@ private:
 	void transform_button_clicked();
 };
 
-#endif /* __midi_region_operations_box_h__ */
diff --git a/gtk2_ardour/midi_region_properties_box.h b/gtk2_ardour/midi_region_properties_box.h
index 2360c8a8c5..8488a2b65b 100644
--- a/gtk2_ardour/midi_region_properties_box.h
+++ b/gtk2_ardour/midi_region_properties_box.h
@@ -17,8 +17,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __midi_region_properties_box_h__
-#define __midi_region_properties_box_h__
+#pragma once
 
 #include <map>
 
@@ -56,4 +55,3 @@ private:
 	ArdourWidgets::ArdourButton cc_selector_button;
 };
 
-#endif /* __midi_region_properties_box_h__ */
diff --git a/gtk2_ardour/midi_region_view.h b/gtk2_ardour/midi_region_view.h
index e204f10c2a..929b90adaf 100644
--- a/gtk2_ardour/midi_region_view.h
+++ b/gtk2_ardour/midi_region_view.h
@@ -22,8 +22,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_midi_region_view_h__
-#define __gtk_ardour_midi_region_view_h__
+#pragma once
 
 #include <string>
 #include <vector>
@@ -176,4 +175,3 @@ public:
 };
 
 
-#endif /* __gtk_ardour_midi_region_view_h__ */
diff --git a/gtk2_ardour/midi_selection.h b/gtk2_ardour/midi_selection.h
index 28ac932c63..68cddaa008 100644
--- a/gtk2_ardour/midi_selection.h
+++ b/gtk2_ardour/midi_selection.h
@@ -17,8 +17,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_gtk_midi_selection_h__
-#define __ardour_gtk_midi_selection_h__
+#pragma once
 
 #include "region_selection.h"
 
@@ -49,4 +48,3 @@ public:
 	}
 };
 
-#endif /* __ardour_gtk_midi_selection_h__ */
diff --git a/gtk2_ardour/midi_streamview.h b/gtk2_ardour/midi_streamview.h
index 6d60ce699b..31550a66cb 100644
--- a/gtk2_ardour/midi_streamview.h
+++ b/gtk2_ardour/midi_streamview.h
@@ -20,8 +20,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_midi_streamview_h__
-#define __ardour_midi_streamview_h__
+#pragma once
 
 #include <list>
 #include <cmath>
@@ -115,4 +114,3 @@ private:
 	bool _updates_suspended;
 };
 
-#endif /* __ardour_midi_streamview_h__ */
diff --git a/gtk2_ardour/midi_time_axis.h b/gtk2_ardour/midi_time_axis.h
index 4b53cff4e7..d89646d079 100644
--- a/gtk2_ardour/midi_time_axis.h
+++ b/gtk2_ardour/midi_time_axis.h
@@ -21,8 +21,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_midi_time_axis_h__
-#define __ardour_midi_time_axis_h__
+#pragma once
 
 #include <list>
 
@@ -212,4 +211,3 @@ private:
 	PBD::ScopedConnection mouse_mode_connection;
 };
 
-#endif /* __ardour_midi_time_axis_h__ */
diff --git a/gtk2_ardour/midi_tracer.h b/gtk2_ardour/midi_tracer.h
index 775ff9cef9..7bc0910c55 100644
--- a/gtk2_ardour/midi_tracer.h
+++ b/gtk2_ardour/midi_tracer.h
@@ -19,8 +19,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_gtk_midi_tracer_h__
-#define __ardour_gtk_midi_tracer_h__
+#pragma once
 
 #include <atomic>
 
@@ -124,4 +123,3 @@ private:
 	static unsigned int window_count;
 };
 
-#endif /* __ardour_gtk_midi_tracer_h__ */
diff --git a/gtk2_ardour/midi_util.h b/gtk2_ardour/midi_util.h
index bbd2800920..aac285fb25 100644
--- a/gtk2_ardour/midi_util.h
+++ b/gtk2_ardour/midi_util.h
@@ -17,8 +17,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_midi_util_h__
-#define __gtk_ardour_midi_util_h__
+#pragma once
 
 inline static void clamp_to_0_127(uint8_t &val)
 {
@@ -29,5 +28,4 @@ inline static void clamp_to_0_127(uint8_t &val)
 	}
 }
 
-#endif /* __gtk_ardour_midi_util_h__ */
 
diff --git a/gtk2_ardour/midi_view.h b/gtk2_ardour/midi_view.h
index 10de1513f3..3255e7d148 100644
--- a/gtk2_ardour/midi_view.h
+++ b/gtk2_ardour/midi_view.h
@@ -22,8 +22,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_midi_view_h__
-#define __gtk_ardour_midi_view_h__
+#pragma once
 
 #include <string>
 #include <vector>
@@ -643,4 +642,3 @@ class MidiView : public virtual sigc::trackable
 };
 
 
-#endif /* __gtk_ardour_midi_view_h__ */
diff --git a/gtk2_ardour/mini_timeline.h b/gtk2_ardour/mini_timeline.h
index 94ec437788..8b408d72a1 100644
--- a/gtk2_ardour/mini_timeline.h
+++ b/gtk2_ardour/mini_timeline.h
@@ -17,8 +17,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtkardour_mini_timeline_h__
-#define __gtkardour_mini_timeline_h__
+#pragma once
 
 #include <list>
 #include <pangomm.h>
@@ -118,4 +117,3 @@ private:
 	JumpList _jumplist;
 };
 
-#endif
diff --git a/gtk2_ardour/missing_file_dialog.h b/gtk2_ardour/missing_file_dialog.h
index 799ad0ebfd..4318612375 100644
--- a/gtk2_ardour/missing_file_dialog.h
+++ b/gtk2_ardour/missing_file_dialog.h
@@ -17,8 +17,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_missing_file_dialog_h__
-#define __gtk_ardour_missing_file_dialog_h__
+#pragma once
 
 #include <string>
 #include <gtkmm/label.h>
@@ -57,4 +56,3 @@ private:
 	void set_absolute ();
 };
 
-#endif /* __gtk_ardour_missing_file_dialog_h__ */
diff --git a/gtk2_ardour/missing_filesource_dialog.h b/gtk2_ardour/missing_filesource_dialog.h
index f9493f4869..b6b7a90b52 100644
--- a/gtk2_ardour/missing_filesource_dialog.h
+++ b/gtk2_ardour/missing_filesource_dialog.h
@@ -17,8 +17,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_missing_filesource_dialog_h__
-#define __gtk_ardour_missing_filesource_dialog_h__
+#pragma once
 
 #include <list>
 #include <string>
@@ -37,4 +36,3 @@ public:
 	MissingFileSourceDialog (Gtk::Window&, ARDOUR::Session*, std::list<std::string> const &, ARDOUR::DataType);
 };
 
-#endif
diff --git a/gtk2_ardour/missing_plugin_dialog.h b/gtk2_ardour/missing_plugin_dialog.h
index 31f1d4b5db..e7569c36be 100644
--- a/gtk2_ardour/missing_plugin_dialog.h
+++ b/gtk2_ardour/missing_plugin_dialog.h
@@ -17,8 +17,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_missing_plugin_dialog_h__
-#define __gtk_ardour_missing_plugin_dialog_h__
+#pragma once
 
 #include <string>
 #include "ardour_dialog.h"
@@ -33,4 +32,3 @@ public:
 	MissingPluginDialog (Gtk::Window&, ARDOUR::Session*, std::list<std::string> const &, bool);
 };
 
-#endif /* __gtk_ardour_missing_plugin_dialog_h__ */
diff --git a/gtk2_ardour/mixer_group_tabs.h b/gtk2_ardour/mixer_group_tabs.h
index daf9426231..a74d6af15d 100644
--- a/gtk2_ardour/mixer_group_tabs.h
+++ b/gtk2_ardour/mixer_group_tabs.h
@@ -17,8 +17,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_mixer_group_tabs_h__
-#define __gtk_ardour_mixer_group_tabs_h__
+#pragma once
 
 #include "group_tabs.h"
 
@@ -44,4 +43,3 @@ private:
 	Mixer_UI* _mixer;
 };
 
-#endif // __gtk_ardour_mixer_group_tabs_h__
diff --git a/gtk2_ardour/mixer_ui.h b/gtk2_ardour/mixer_ui.h
index 8cdd9c3ff7..21de26ebe2 100644
--- a/gtk2_ardour/mixer_ui.h
+++ b/gtk2_ardour/mixer_ui.h
@@ -22,8 +22,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_mixer_ui_h__
-#define __ardour_mixer_ui_h__
+#pragma once
 
 #include <list>
 
@@ -494,4 +493,3 @@ private:
 	void ab_plugins ();
 };
 
-#endif /* __ardour_mixer_ui_h__ */
diff --git a/gtk2_ardour/mono_panner.h b/gtk2_ardour/mono_panner.h
index 4484a0901c..52e4cd6a99 100644
--- a/gtk2_ardour/mono_panner.h
+++ b/gtk2_ardour/mono_panner.h
@@ -18,8 +18,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_mono_panner_h__
-#define __gtk_ardour_mono_panner_h__
+#pragma once
 
 #include <memory>
 
@@ -101,4 +100,3 @@ private:
 	void pannable_handler ();
 };
 
-#endif /* __gtk_ardour_mono_panner_h__ */
diff --git a/gtk2_ardour/mono_panner_editor.h b/gtk2_ardour/mono_panner_editor.h
index f96eff41d7..36715fc038 100644
--- a/gtk2_ardour/mono_panner_editor.h
+++ b/gtk2_ardour/mono_panner_editor.h
@@ -16,8 +16,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_mono_panner_editor_h__
-#define __gtk_ardour_mono_panner_editor_h__
+#pragma once
 
 #include <gtkmm/spinbutton.h>
 #include "panner_editor.h"
@@ -44,4 +43,3 @@ private:
 	PBD::ScopedConnectionList _connections;
 };
 
-#endif // __gtk_ardour_mono_panner_editor_h__
diff --git a/gtk2_ardour/multi_region_properties_box.h b/gtk2_ardour/multi_region_properties_box.h
index 25bf1c0930..8bdbc5dafb 100644
--- a/gtk2_ardour/multi_region_properties_box.h
+++ b/gtk2_ardour/multi_region_properties_box.h
@@ -17,8 +17,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __multi_region_properties_box_h__
-#define __multi_region_properties_box_h__
+#pragma once
 
 #include <map>
 
@@ -65,4 +64,3 @@ private:
 	void unmute_selected_regions();
 };
 
-#endif /* __multi_region_properties_box_h__ */
diff --git a/gtk2_ardour/nag.h b/gtk2_ardour/nag.h
index f09f9c2670..2714ce1c9c 100644
--- a/gtk2_ardour/nag.h
+++ b/gtk2_ardour/nag.h
@@ -16,8 +16,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_nag_h__
-#define __gtk_ardour_nag_h__
+#pragma once
 
 #include "ardour_dialog.h"
 
@@ -53,4 +52,3 @@ private:
 	static bool is_subscribed (bool& really);
 };
 
-#endif /* __gtk_ardour_nag_h__ */
diff --git a/gtk2_ardour/note.h b/gtk2_ardour/note.h
index 08bb283590..d4f37ade97 100644
--- a/gtk2_ardour/note.h
+++ b/gtk2_ardour/note.h
@@ -16,8 +16,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_note_h__
-#define __gtk_ardour_note_h__
+#pragma once
 
 #include <iostream>
 
@@ -74,4 +73,3 @@ private:
 	ArdourCanvas::Note* _visual_note;
 };
 
-#endif /* __gtk_ardour_note_h__ */
diff --git a/gtk2_ardour/note_base.h b/gtk2_ardour/note_base.h
index b548fb80d8..22e0b637c4 100644
--- a/gtk2_ardour/note_base.h
+++ b/gtk2_ardour/note_base.h
@@ -18,8 +18,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_note_base_h__
-#define __gtk_ardour_note_base_h__
+#pragma once
 
 #include <memory>
 
@@ -162,4 +161,3 @@ private:
 	static bool _color_init;
 };
 
-#endif /* __gtk_ardour_note_h__ */
diff --git a/gtk2_ardour/option_editor.h b/gtk2_ardour/option_editor.h
index db622a5b7f..eac9a48e46 100644
--- a/gtk2_ardour/option_editor.h
+++ b/gtk2_ardour/option_editor.h
@@ -22,8 +22,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_option_editor_h__
-#define __gtk_ardour_option_editor_h__
+#pragma once
 
 #include <gtkmm/checkbutton.h>
 #include <gtkmm/comboboxtext.h>
@@ -804,4 +803,3 @@ protected:
 	Gtk::HBox hpacker;
 };
 
-#endif /* __gtk_ardour_option_editor_h__ */
diff --git a/gtk2_ardour/opts.h b/gtk2_ardour/opts.h
index aa47b30b23..56e0b2c031 100644
--- a/gtk2_ardour/opts.h
+++ b/gtk2_ardour/opts.h
@@ -18,8 +18,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_opts_h__
-#define __ardour_opts_h__
+#pragma once
 
 #include <string>
 
@@ -45,4 +44,3 @@ extern int32_t parse_opts (int argc, char *argv[]);
 
 }
 
-#endif /* __ardour_opts_h__ */
diff --git a/gtk2_ardour/panner_editor.h b/gtk2_ardour/panner_editor.h
index 4217756082..104e7b1c0a 100644
--- a/gtk2_ardour/panner_editor.h
+++ b/gtk2_ardour/panner_editor.h
@@ -17,8 +17,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_panner_editor_h__
-#define __gtk_ardour_panner_editor_h__
+#pragma once
 
 #include "ardour_dialog.h"
 
@@ -31,4 +30,3 @@ private:
 	void close_button_clicked ();
 };
 
-#endif // __gtk_ardour_panner_editor_h__
diff --git a/gtk2_ardour/panner_interface.h b/gtk2_ardour/panner_interface.h
index 53d3e472af..85e098317a 100644
--- a/gtk2_ardour/panner_interface.h
+++ b/gtk2_ardour/panner_interface.h
@@ -17,8 +17,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_panner_interface_h__
-#define __gtk_ardour_panner_interface_h__
+#pragma once
 
 #include <memory>
 
@@ -89,4 +88,3 @@ private:
 	PannerEditor* _editor;
 };
 
-#endif
diff --git a/gtk2_ardour/panner_ui.h b/gtk2_ardour/panner_ui.h
index c128de5911..58bf916dc2 100644
--- a/gtk2_ardour/panner_ui.h
+++ b/gtk2_ardour/panner_ui.h
@@ -20,8 +20,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_gtk_panner_ui_h__
-#define __ardour_gtk_panner_ui_h__
+#pragma once
 
 #include <vector>
 
@@ -153,5 +152,4 @@ private:
 	bool _suspend_menu_callbacks;
 };
 
-#endif /* __ardour_gtk_panner_ui_h__ */
 
diff --git a/gtk2_ardour/paste_context.h b/gtk2_ardour/paste_context.h
index 8633960d96..295518723f 100644
--- a/gtk2_ardour/paste_context.h
+++ b/gtk2_ardour/paste_context.h
@@ -16,8 +16,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_paste_context_h__
-#define __ardour_paste_context_h__
+#pragma once
 
 #include "item_counts.h"
 
@@ -37,4 +36,3 @@ public:
 	bool       greedy;  ///< If true, greedily steal items that don't match
 };
 
-#endif /* __ardour_paste_context_h__ */
diff --git a/gtk2_ardour/patch_change_widget.h b/gtk2_ardour/patch_change_widget.h
index 48c1a0a3e3..57fc2b805e 100644
--- a/gtk2_ardour/patch_change_widget.h
+++ b/gtk2_ardour/patch_change_widget.h
@@ -16,8 +16,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtkardour_patch_change_widget_h__
-#define __gtkardour_patch_change_widget_h__
+#pragma once
 
 #include <gtkmm/box.h>
 #include <gtkmm/notebook.h>
@@ -212,4 +211,3 @@ private:
 	PatchChangeWidget     w;
 };
 
-#endif
diff --git a/gtk2_ardour/piano_roll_header.h b/gtk2_ardour/piano_roll_header.h
index 279b4ed48c..dab1f28c44 100644
--- a/gtk2_ardour/piano_roll_header.h
+++ b/gtk2_ardour/piano_roll_header.h
@@ -17,8 +17,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_piano_roll_header_h__
-#define __ardour_piano_roll_header_h__
+#pragma once
 
 #include "ardour/types.h"
 
@@ -129,4 +128,3 @@ private:
 	bool show_scroomer () const;
 };
 
-#endif /* __ardour_piano_roll_header_h__ */
diff --git a/gtk2_ardour/pingback.h b/gtk2_ardour/pingback.h
index 82c909cb4e..d83bafce55 100644
--- a/gtk2_ardour/pingback.h
+++ b/gtk2_ardour/pingback.h
@@ -16,12 +16,10 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ui_pingback_h__
-#define __gtk_ui_pingback_h__
+#pragma once
 
 namespace ARDOUR {
 	void pingback (const std::string& this_version,
 		       const std::string& announce_path);
 };
 
-#endif /* __gtk_ui_pingback_h__ */
diff --git a/gtk2_ardour/playlist_selection.h b/gtk2_ardour/playlist_selection.h
index 540e2f93a2..0773445468 100644
--- a/gtk2_ardour/playlist_selection.h
+++ b/gtk2_ardour/playlist_selection.h
@@ -17,8 +17,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_gtk_playlist_selection_h__
-#define __ardour_gtk_playlist_selection_h__
+#pragma once
 
 #include "ardour/playlist.h"
 
@@ -41,4 +40,3 @@ public:
 	}
 };
 
-#endif /* __ardour_gtk_playlist_selection_h__ */
diff --git a/gtk2_ardour/playlist_selector.h b/gtk2_ardour/playlist_selector.h
index 21ffa9ecc6..43b861cfc1 100644
--- a/gtk2_ardour/playlist_selector.h
+++ b/gtk2_ardour/playlist_selector.h
@@ -18,8 +18,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_playlist_selector_h__
-#define __ardour_playlist_selector_h__
+#pragma once
 
 #include <memory>
 
@@ -123,4 +122,3 @@ private:
 	bool _ignore_selection;
 };
 
-#endif // __ardour_playlist_selector_h__
diff --git a/gtk2_ardour/plugin_dspload_window.h b/gtk2_ardour/plugin_dspload_window.h
index 9c9d9388a6..e6176b30fa 100644
--- a/gtk2_ardour/plugin_dspload_window.h
+++ b/gtk2_ardour/plugin_dspload_window.h
@@ -16,8 +16,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_plugin_dspload_window_h__
-#define __ardour_plugin_dspload_window_h__
+#pragma once
 
 #include <memory>
 
@@ -70,5 +69,4 @@ private:
 	PBD::ScopedConnectionList _processor_connections;
 	PBD::ScopedConnectionList _route_connections;
 };
-#endif
 
diff --git a/gtk2_ardour/plugin_interest.h b/gtk2_ardour/plugin_interest.h
index 049f4b9adc..d093a96cee 100644
--- a/gtk2_ardour/plugin_interest.h
+++ b/gtk2_ardour/plugin_interest.h
@@ -16,8 +16,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtkardour_plugin_interest_h__
-#define __gtkardour_plugin_interest_h__
+#pragma once
 
 #include <vector>
 #include "ardour/plugin.h"
@@ -33,4 +32,3 @@ public:
 	virtual bool use_plugins (const SelectedPlugins&) = 0;
 };
 
-#endif /* __gtkardour_plugin_interest_h__ */
diff --git a/gtk2_ardour/plugin_pin_dialog.h b/gtk2_ardour/plugin_pin_dialog.h
index ea42dd26bf..1088c48991 100644
--- a/gtk2_ardour/plugin_pin_dialog.h
+++ b/gtk2_ardour/plugin_pin_dialog.h
@@ -16,8 +16,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtkardour_plugin_pin_dialog_h__
-#define __gtkardour_plugin_pin_dialog_h__
+#pragma once
 
 #include <gtkmm/drawingarea.h>
 
@@ -267,4 +266,3 @@ private:
 	bool _height_mapped;
 };
 
-#endif
diff --git a/gtk2_ardour/plugin_selector.h b/gtk2_ardour/plugin_selector.h
index 4f16688ae7..1aa8e2bec6 100644
--- a/gtk2_ardour/plugin_selector.h
+++ b/gtk2_ardour/plugin_selector.h
@@ -22,8 +22,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_plugin_selector_h__
-#define __ardour_plugin_selector_h__
+#pragma once
 
 #include <gtkmm/button.h>
 #include <gtkmm/checkbutton.h>
@@ -190,4 +189,3 @@ private:
 	bool _inhibit_refill;
 };
 
-#endif // __ardour_plugin_selector_h__
diff --git a/gtk2_ardour/plugin_setup_dialog.h b/gtk2_ardour/plugin_setup_dialog.h
index 5fb305c4ae..fb6cf96ebc 100644
--- a/gtk2_ardour/plugin_setup_dialog.h
+++ b/gtk2_ardour/plugin_setup_dialog.h
@@ -16,8 +16,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtkardour_plugin_setup_dialog_h__
-#define __gtkardour_plugin_setup_dialog_h__
+#pragma once
 
 #include "ardour/plugin_insert.h"
 #include "ardour/route.h"
@@ -55,4 +54,3 @@ private:
 	ARDOUR::ChanCount _cur_outputs;
 };
 
-#endif
diff --git a/gtk2_ardour/plugin_ui.h b/gtk2_ardour/plugin_ui.h
index d4a38259da..4503c30bd8 100644
--- a/gtk2_ardour/plugin_ui.h
+++ b/gtk2_ardour/plugin_ui.h
@@ -22,8 +22,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_plugin_ui_h__
-#define __ardour_plugin_ui_h__
+#pragma once
 
 #ifdef WAF_BUILD
 #include "gtk2ardour-config.h"
@@ -411,4 +410,3 @@ extern VSTPluginUI* create_mac_vst_gui (std::shared_ptr<ARDOUR::PlugInsertBase>)
 extern PlugUIBase* create_au_gui (std::shared_ptr<ARDOUR::PlugInsertBase>, Gtk::VBox**);
 #endif
 
-#endif /* __ardour_plugin_ui_h__ */
diff --git a/gtk2_ardour/plugin_utils.h b/gtk2_ardour/plugin_utils.h
index d93c87b08b..de8ccafdb1 100644
--- a/gtk2_ardour/plugin_utils.h
+++ b/gtk2_ardour/plugin_utils.h
@@ -16,8 +16,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtkardour_plugin_utils_h__
-#define __gtkardour_plugin_utils_h__
+#pragma once
 
 #include <list>
 #include <string>
@@ -139,4 +138,3 @@ private:
 };
 
 } // namespace ARDOUR_PLUGIN_UTILS
-#endif
diff --git a/gtk2_ardour/point_selection.h b/gtk2_ardour/point_selection.h
index de818ae87b..8c265ceb7c 100644
--- a/gtk2_ardour/point_selection.h
+++ b/gtk2_ardour/point_selection.h
@@ -18,8 +18,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_gtk_point_selection_h__
-#define __ardour_gtk_point_selection_h__
+#pragma once
 
 #include <list>
 
@@ -29,4 +28,3 @@ class PointSelection : public std::list<ControlPoint *>
 {
 };
 
-#endif /* __ardour_gtk_point_selection_h__ */
diff --git a/gtk2_ardour/port_group.h b/gtk2_ardour/port_group.h
index 74767144d4..690ee00f13 100644
--- a/gtk2_ardour/port_group.h
+++ b/gtk2_ardour/port_group.h
@@ -18,8 +18,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef  __gtk_ardour_port_group_h__
-#define  __gtk_ardour_port_group_h__
+#pragma once
 
 #include <memory>
 #include <set>
@@ -157,4 +156,3 @@ private:
 	ARDOUR::Bundle::Change _pending_bundle_change;
 };
 
-#endif /* __gtk_ardour_port_group_h__ */
diff --git a/gtk2_ardour/port_insert_ui.h b/gtk2_ardour/port_insert_ui.h
index 94f4188419..bdbc5f04de 100644
--- a/gtk2_ardour/port_insert_ui.h
+++ b/gtk2_ardour/port_insert_ui.h
@@ -16,8 +16,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtkardour_port_insert_ui_h__
-#define __gtkardour_port_insert_ui_h__
+#pragma once
 
 #include "widgets/ardour_button.h"
 #include "widgets/stateful_button.h"
@@ -97,4 +96,3 @@ private:
 	PortInsertUI _portinsertui;
 };
 
-#endif /* __gtkardour_port_insert_ui_h__ */
diff --git a/gtk2_ardour/port_matrix.h b/gtk2_ardour/port_matrix.h
index 1a74cd38e6..4074dbd5ff 100644
--- a/gtk2_ardour/port_matrix.h
+++ b/gtk2_ardour/port_matrix.h
@@ -18,8 +18,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_port_matrix_h__
-#define __gtk_ardour_port_matrix_h__
+#pragma once
 
 #include <list>
 #include <memory>
@@ -239,4 +238,3 @@ private:
 	bool _ignore_notebook_page_selected;
 };
 
-#endif
diff --git a/gtk2_ardour/port_matrix_body.h b/gtk2_ardour/port_matrix_body.h
index 2d426d288f..c2b7ae16d6 100644
--- a/gtk2_ardour/port_matrix_body.h
+++ b/gtk2_ardour/port_matrix_body.h
@@ -16,8 +16,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_port_matrix_body_h__
-#define __gtk_ardour_port_matrix_body_h__
+#pragma once
 
 #include <gtkmm/eventbox.h>
 #include "port_group.h"
@@ -106,4 +105,3 @@ private:
 	PBD::ScopedConnectionList _bundle_connections;
 };
 
-#endif
diff --git a/gtk2_ardour/port_matrix_column_labels.h b/gtk2_ardour/port_matrix_column_labels.h
index 21665e67eb..b2e463f013 100644
--- a/gtk2_ardour/port_matrix_column_labels.h
+++ b/gtk2_ardour/port_matrix_column_labels.h
@@ -16,8 +16,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __port_matrix_column_labels_h__
-#define __port_matrix_column_labels_h__
+#pragma once
 
 #include <memory>
 
@@ -69,4 +68,3 @@ private:
 	uint32_t _overhang;
 };
 
-#endif
diff --git a/gtk2_ardour/port_matrix_component.h b/gtk2_ardour/port_matrix_component.h
index cf745d0874..cbaaaa6478 100644
--- a/gtk2_ardour/port_matrix_component.h
+++ b/gtk2_ardour/port_matrix_component.h
@@ -16,8 +16,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_port_matrix_component_h__
-#define __gtk_ardour_port_matrix_component_h__
+#pragma once
 
 #include <cstdint>
 #include <memory>
@@ -193,4 +192,3 @@ private:
 	bool _dimension_computation_required; ///< true if the dimensions are out of date
 };
 
-#endif
diff --git a/gtk2_ardour/port_matrix_grid.h b/gtk2_ardour/port_matrix_grid.h
index 21f98e2e91..0d1d46b022 100644
--- a/gtk2_ardour/port_matrix_grid.h
+++ b/gtk2_ardour/port_matrix_grid.h
@@ -16,8 +16,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef  __gtk_ardour_port_matrix_grid_h__
-#define  __gtk_ardour_port_matrix_grid_h__
+#pragma once
 
 #include <memory>
 #include <string>
@@ -72,4 +71,3 @@ private:
 	int _drag_y;
 };
 
-#endif
diff --git a/gtk2_ardour/port_matrix_labels.h b/gtk2_ardour/port_matrix_labels.h
index abee76737d..be64e6b306 100644
--- a/gtk2_ardour/port_matrix_labels.h
+++ b/gtk2_ardour/port_matrix_labels.h
@@ -16,8 +16,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __port_matrix_labels_h__
-#define __port_matrix_labels_h__
+#pragma once
 
 #include "port_matrix_component.h"
 
@@ -46,4 +45,3 @@ private:
 	std::vector<ARDOUR::BundleChannel> _channel_highlights;
 };
 
-#endif
diff --git a/gtk2_ardour/port_matrix_row_labels.h b/gtk2_ardour/port_matrix_row_labels.h
index c8d204b055..c2d6fc069a 100644
--- a/gtk2_ardour/port_matrix_row_labels.h
+++ b/gtk2_ardour/port_matrix_row_labels.h
@@ -16,8 +16,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __port_matrix_row_labels_h__
-#define __port_matrix_row_labels_h__
+#pragma once
 
 #include <memory>
 
@@ -73,4 +72,3 @@ private:
 	PortMatrixColumnLabels& _column_labels;
 };
 
-#endif
diff --git a/gtk2_ardour/port_matrix_types.h b/gtk2_ardour/port_matrix_types.h
index ca00b47146..a14d5542d3 100644
--- a/gtk2_ardour/port_matrix_types.h
+++ b/gtk2_ardour/port_matrix_types.h
@@ -17,8 +17,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_gtk_port_matrix_types_h__
-#define __ardour_gtk_port_matrix_types_h__
+#pragma once
 
 #include "ardour/bundle.h"
 
@@ -45,4 +44,3 @@ public:
 	};
 };
 
-#endif
diff --git a/gtk2_ardour/prh.h b/gtk2_ardour/prh.h
index 7f8c93f51c..fc9a7f6215 100644
--- a/gtk2_ardour/prh.h
+++ b/gtk2_ardour/prh.h
@@ -17,8 +17,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_canvas_piano_roll_header_h__
-#define __ardour_canvas_piano_roll_header_h__
+#pragma once
 
 #include <pangomm/layout.h>
 #include <glibmm/refptr.h>
@@ -132,4 +131,3 @@ private:
 
 }
 
-#endif /* __ardour_piano_roll_header_h__ */
diff --git a/gtk2_ardour/processor_selection.h b/gtk2_ardour/processor_selection.h
index 6c7eb3be2b..cdf14c66e2 100644
--- a/gtk2_ardour/processor_selection.h
+++ b/gtk2_ardour/processor_selection.h
@@ -17,8 +17,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_gtk_processor_selection_h__
-#define __ardour_gtk_processor_selection_h__
+#pragma once
 
 #include <vector>
 
@@ -83,4 +82,3 @@ class ProcessorSelection : public PBD::ScopedConnectionList, public sigc::tracka
 
 bool operator==(const ProcessorSelection& a, const ProcessorSelection& b);
 
-#endif /* __ardour_gtk_processor_selection_h__ */
diff --git a/gtk2_ardour/progress_reporter.h b/gtk2_ardour/progress_reporter.h
index 19048c8afa..79ba555c41 100644
--- a/gtk2_ardour/progress_reporter.h
+++ b/gtk2_ardour/progress_reporter.h
@@ -16,8 +16,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_progress_reporter_h__
-#define __ardour_progress_reporter_h__
+#pragma once
 
 #include "pbd/progress.h"
 
@@ -38,4 +37,3 @@ private:
 	int _p;
 };
 
-#endif
diff --git a/gtk2_ardour/pt_import_selector.h b/gtk2_ardour/pt_import_selector.h
index e54a339bb7..c8cee07c82 100644
--- a/gtk2_ardour/pt_import_selector.h
+++ b/gtk2_ardour/pt_import_selector.h
@@ -15,8 +15,7 @@
  * with this program; if not, write to the Free Software Foundation, Inc.,
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
-#ifndef __pt_import_selector_h__
-#define __pt_import_selector_h__
+#pragma once
 
 #include <string>
 #include <stdio.h>
@@ -50,4 +49,3 @@ private:
 	Gtk::Button ptimport_cancel_button;
 };
 
-#endif
diff --git a/gtk2_ardour/public_editor.h b/gtk2_ardour/public_editor.h
index 3d21cd979f..1225db9448 100644
--- a/gtk2_ardour/public_editor.h
+++ b/gtk2_ardour/public_editor.h
@@ -25,8 +25,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_public_editor_h__
-#define __gtk_ardour_public_editor_h__
+#pragma once
 
 #ifdef WAF_BUILD
 #include "gtk2ardour-config.h"
@@ -495,4 +494,3 @@ public:
 	}
 };
 
-#endif // __gtk_ardour_public_editor_h__
diff --git a/gtk2_ardour/rc_option_editor.h b/gtk2_ardour/rc_option_editor.h
index 13cecb3920..b617c784b9 100644
--- a/gtk2_ardour/rc_option_editor.h
+++ b/gtk2_ardour/rc_option_editor.h
@@ -18,8 +18,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_rc_option_editor_h__
-#define __gtk_ardour_rc_option_editor_h__
+#pragma once
 
 #include "widgets/tabbable.h"
 
@@ -90,5 +89,4 @@ private:
 	void edit_vst_path (std::string const&, std::string const&, sigc::slot<std::string>, sigc::slot<bool, std::string>);
 };
 
-#endif /* __gtk_ardour_rc_option_editor_h__ */
 
diff --git a/gtk2_ardour/recorder_group_tabs.h b/gtk2_ardour/recorder_group_tabs.h
index 04a9641b28..a685d287c9 100644
--- a/gtk2_ardour/recorder_group_tabs.h
+++ b/gtk2_ardour/recorder_group_tabs.h
@@ -16,8 +16,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_recorder_group_tabs_h__
-#define __gtk_ardour_recorder_group_tabs_h__
+#pragma once
 
 #include "group_tabs.h"
 
@@ -39,4 +38,3 @@ private:
 	RecorderUI* _recorder;
 };
 
-#endif /* __gtk_ardour_recorder_ui_h__ */
diff --git a/gtk2_ardour/recorder_ui.h b/gtk2_ardour/recorder_ui.h
index c6807ba172..8d3eee18e5 100644
--- a/gtk2_ardour/recorder_ui.h
+++ b/gtk2_ardour/recorder_ui.h
@@ -16,8 +16,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_recorder_ui_h__
-#define __gtk_ardour_recorder_ui_h__
+#pragma once
 
 #include <list>
 #include <memory>
@@ -281,4 +280,3 @@ public:
 	std::list<TrackRecordAxis*> visible_recorders () const;
 };
 
-#endif /* __gtk_ardour_recorder_ui_h__ */
diff --git a/gtk2_ardour/region_editor.h b/gtk2_ardour/region_editor.h
index 86952592f3..b53d71391a 100644
--- a/gtk2_ardour/region_editor.h
+++ b/gtk2_ardour/region_editor.h
@@ -19,8 +19,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_region_edit_h__
-#define __gtk_ardour_region_edit_h__
+#pragma once
 
 #include <map>
 
@@ -197,4 +196,3 @@ private:
 	void set_clock_mode_from_primary ();
 };
 
-#endif /* __gtk_ardour_region_edit_h__ */
diff --git a/gtk2_ardour/region_fx_line.h b/gtk2_ardour/region_fx_line.h
index b1e45f9c3a..ec218554d8 100644
--- a/gtk2_ardour/region_fx_line.h
+++ b/gtk2_ardour/region_fx_line.h
@@ -16,8 +16,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_gtk_region_fx_line_h__
-#define __ardour_gtk_region_fx_line_h__
+#pragma once
 
 #include "editor_automation_line.h"
 
@@ -47,4 +46,3 @@ private:
 	PBD::ScopedConnection                    _region_changed_connection;
 };
 
-#endif
diff --git a/gtk2_ardour/region_gain_line.h b/gtk2_ardour/region_gain_line.h
index 34780ff3e5..ce9162c050 100644
--- a/gtk2_ardour/region_gain_line.h
+++ b/gtk2_ardour/region_gain_line.h
@@ -22,8 +22,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_gtk_region_gain_line_h__
-#define __ardour_gtk_region_gain_line_h__
+#pragma once
 
 #include "ardour/ardour.h"
 
@@ -53,4 +52,3 @@ private:
 	AudioRegionView& arv;
 };
 
-#endif /* __ardour_gtk_region_gain_line_h__ */
diff --git a/gtk2_ardour/region_properties_box.h b/gtk2_ardour/region_properties_box.h
index 16fbd734b0..63cbc156c1 100644
--- a/gtk2_ardour/region_properties_box.h
+++ b/gtk2_ardour/region_properties_box.h
@@ -17,8 +17,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __midi_region_properties_box_h__
-#define __midi_region_properties_box_h__
+#pragma once
 
 #include <map>
 
@@ -48,4 +47,3 @@ private:
 	Gtk::Table table;
 };
 
-#endif /* __midi_region_properties_box_h__ */
diff --git a/gtk2_ardour/region_selection.h b/gtk2_ardour/region_selection.h
index a27ae2b9a8..df6f1cdd2d 100644
--- a/gtk2_ardour/region_selection.h
+++ b/gtk2_ardour/region_selection.h
@@ -20,8 +20,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_gtk_region_selection_h__
-#define __ardour_gtk_region_selection_h__
+#pragma once
 
 #include <set>
 #include <list>
@@ -77,4 +76,3 @@ private:
 	std::list<RegionView *> _bylayer; ///< list of regions sorted by layer
 };
 
-#endif /* __ardour_gtk_region_selection_h__ */
diff --git a/gtk2_ardour/region_view.h b/gtk2_ardour/region_view.h
index fda4ea3b47..a0f18310d3 100644
--- a/gtk2_ardour/region_view.h
+++ b/gtk2_ardour/region_view.h
@@ -21,8 +21,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_region_view_h__
-#define __gtk_ardour_region_view_h__
+#pragma once
 
 #ifdef interface
 #undef interface
@@ -260,4 +259,3 @@ private:
 
 };
 
-#endif /* __gtk_ardour_region_view_h__ */
diff --git a/gtk2_ardour/return_ui.h b/gtk2_ardour/return_ui.h
index 6e61060cbf..dd52181e37 100644
--- a/gtk2_ardour/return_ui.h
+++ b/gtk2_ardour/return_ui.h
@@ -18,8 +18,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_gtk_return_ui_h__
-#define __ardour_gtk_return_ui_h__
+#pragma once
 
 #include "gain_meter.h"
 #include "panner_ui.h"
@@ -72,5 +71,4 @@ class ReturnUIWindow : public ArdourWindow
 	PBD::ScopedConnection going_away_connection;
 };
 
-#endif /* __ardour_gtk_return_ui_h__ */
 
diff --git a/gtk2_ardour/rgb_macros.h b/gtk2_ardour/rgb_macros.h
index ffc48ccbe4..ecacc99eee 100644
--- a/gtk2_ardour/rgb_macros.h
+++ b/gtk2_ardour/rgb_macros.h
@@ -17,9 +17,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_rgb_macros_h__
-#define __gtk_ardour_rgb_macros_h__
+#pragma once
 
 #include "gtkmm2ext/rgb_macros.h"
 
-#endif /* __gtk_ardour_rgb_macros_h__ */
diff --git a/gtk2_ardour/route_dialogs.h b/gtk2_ardour/route_dialogs.h
index 848adbfc3a..6cf513b179 100644
--- a/gtk2_ardour/route_dialogs.h
+++ b/gtk2_ardour/route_dialogs.h
@@ -16,8 +16,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_route_dialogs_h__
-#define __gtk_ardour_route_dialogs_h__
+#pragma once
 
 namespace RouteDialogs {
 
@@ -30,4 +29,3 @@ enum InsertAt {
 
 }
 
-#endif /* __gtk_ardour_route_dialogs_h__ */
diff --git a/gtk2_ardour/route_group_dialog.h b/gtk2_ardour/route_group_dialog.h
index baa4ae84fd..84fac50b6e 100644
--- a/gtk2_ardour/route_group_dialog.h
+++ b/gtk2_ardour/route_group_dialog.h
@@ -19,8 +19,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_route_group_dialog_h__
-#define __gtk_ardour_route_group_dialog_h__
+#pragma once
 
 #include <gtkmm/dialog.h>
 #include <gtkmm/entry.h>
@@ -67,4 +66,3 @@ private:
 	PBD::ScopedConnection _group_connection;
 };
 
-#endif
diff --git a/gtk2_ardour/route_group_menu.h b/gtk2_ardour/route_group_menu.h
index 16f58bb63d..1f9b201abe 100644
--- a/gtk2_ardour/route_group_menu.h
+++ b/gtk2_ardour/route_group_menu.h
@@ -17,8 +17,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_gtk_route_group_menu_h__
-#define __ardour_gtk_route_group_menu_h__
+#pragma once
 
 #include "ardour/route_group.h"
 #include "ardour/session_handle.h"
@@ -49,4 +48,3 @@ public:
 	ARDOUR::WeakRouteList _subject;
 };
 
-#endif /* __ardour_gtk_route_group_menu_h__ */
diff --git a/gtk2_ardour/route_params_ui.h b/gtk2_ardour/route_params_ui.h
index 0621305202..c33f21af9e 100644
--- a/gtk2_ardour/route_params_ui.h
+++ b/gtk2_ardour/route_params_ui.h
@@ -20,8 +20,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_route_params_ui_h__
-#define __ardour_route_params_ui_h__
+#pragma once
 
 #include <list>
 
@@ -177,4 +176,3 @@ private:
 };
 
 
-#endif /* __ardour_route_params_ui_h__ */
diff --git a/gtk2_ardour/route_processor_selection.h b/gtk2_ardour/route_processor_selection.h
index af2b0909ea..8c2699d3d2 100644
--- a/gtk2_ardour/route_processor_selection.h
+++ b/gtk2_ardour/route_processor_selection.h
@@ -18,8 +18,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_gtk_route_processor_selection_h__
-#define __ardour_gtk_route_processor_selection_h__
+#pragma once
 
 #include <vector>
 #include "pbd/signals.h"
@@ -63,4 +62,3 @@ private:
 
 bool operator==(const RouteProcessorSelection& a, const RouteProcessorSelection& b);
 
-#endif /* __ardour_gtk_route_processor_selection_h__ */
diff --git a/gtk2_ardour/route_time_axis.h b/gtk2_ardour/route_time_axis.h
index eb709a21d0..0cb64f7081 100644
--- a/gtk2_ardour/route_time_axis.h
+++ b/gtk2_ardour/route_time_axis.h
@@ -22,8 +22,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_route_time_axis_h__
-#define __ardour_route_time_axis_h__
+#pragma once
 
 #include <list>
 #include <set>
@@ -311,4 +310,3 @@ private:
 	sigc::connection      ctrl_autohide_connection;
 };
 
-#endif /* __ardour_route_time_axis_h__ */
diff --git a/gtk2_ardour/route_ui_selection.h b/gtk2_ardour/route_ui_selection.h
index 06cfdc9578..de11ae125f 100644
--- a/gtk2_ardour/route_ui_selection.h
+++ b/gtk2_ardour/route_ui_selection.h
@@ -16,8 +16,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_gtk_route_ui_selection_h__
-#define __ardour_gtk_route_ui_selection_h__
+#pragma once
 
 
 #include <set>
@@ -26,4 +25,3 @@ class AxisView;
 
 struct AxisViewSelection : std::set<AxisView*> {};
 
-#endif /* __ardour_gtk_route_ui_selection_h__ */
diff --git a/gtk2_ardour/ruler_dialog.h b/gtk2_ardour/ruler_dialog.h
index 7984194bcb..968d934fd9 100644
--- a/gtk2_ardour/ruler_dialog.h
+++ b/gtk2_ardour/ruler_dialog.h
@@ -17,7 +17,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_ruler_h__
+#pragma once
 #define __gtk_ardour_ruler _h__
 
 #include <string>
@@ -49,4 +49,3 @@ private:
 	void connect_action (Gtk::CheckButton& button, std::string const &action_name_part);
 };
 
-#endif /* __gtk_ardour_add_route_dialog_h__ */
diff --git a/gtk2_ardour/save_as_dialog.h b/gtk2_ardour/save_as_dialog.h
index b07cdead60..b3bbe7cd47 100644
--- a/gtk2_ardour/save_as_dialog.h
+++ b/gtk2_ardour/save_as_dialog.h
@@ -17,8 +17,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_gtk_save_as_dialog_h__
-#define __ardour_gtk_save_as_dialog_h__
+#pragma once
 
 #include <gtkmm/entry.h>
 #include <gtkmm/checkbutton.h>
@@ -54,4 +53,3 @@ private:
 	void no_include_toggled ();
 };
 
-#endif /* __ardour_gtk_tempo_dialog_h__ */
diff --git a/gtk2_ardour/save_template_dialog.h b/gtk2_ardour/save_template_dialog.h
index 4e46e8e971..6a48930963 100644
--- a/gtk2_ardour/save_template_dialog.h
+++ b/gtk2_ardour/save_template_dialog.h
@@ -16,8 +16,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_gtk_save_template_dialog_h__
-#define __ardour_gtk_save_template_dialog_h__
+#pragma once
 
 #include <string>
 
@@ -40,4 +39,3 @@ private:
 	Gtk::TextView _description_editor;
 };
 
-#endif /* __ardour_gtk_save_template_dialog_h__ */
diff --git a/gtk2_ardour/search_path_option.h b/gtk2_ardour/search_path_option.h
index 13153b650a..998de3394f 100644
--- a/gtk2_ardour/search_path_option.h
+++ b/gtk2_ardour/search_path_option.h
@@ -16,8 +16,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_search_path_option_h__
-#define __gtk_ardour_search_path_option_h__
+#pragma once
 
 #include <string>
 
@@ -69,4 +68,3 @@ protected:
 	void path_chosen ();
 };
 
-#endif /* __gtk_ardour_search_path_option_h__ */
diff --git a/gtk2_ardour/selectable.h b/gtk2_ardour/selectable.h
index 1d7d832cca..ee7eb55151 100644
--- a/gtk2_ardour/selectable.h
+++ b/gtk2_ardour/selectable.h
@@ -17,8 +17,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_gtk_selectable_h__
-#define __ardour_gtk_selectable_h__
+#pragma once
 
 #include <sigc++/signal.h>
 
@@ -45,4 +44,3 @@ protected:
 	bool _selected;
 };
 
-#endif /* __ardour_gtk_selectable_h__ */
diff --git a/gtk2_ardour/selection.h b/gtk2_ardour/selection.h
index fd73c4f05a..bcdebf2be2 100644
--- a/gtk2_ardour/selection.h
+++ b/gtk2_ardour/selection.h
@@ -22,8 +22,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_gtk_selection_h__
-#define __ardour_gtk_selection_h__
+#pragma once
 
 #include <memory>
 #include <vector>
@@ -252,4 +251,3 @@ private:
 
 bool operator==(const Selection& a, const Selection& b);
 
-#endif /* __ardour_gtk_selection_h__ */
diff --git a/gtk2_ardour/selection_memento.h b/gtk2_ardour/selection_memento.h
index 6c4e796774..7004a1d35a 100644
--- a/gtk2_ardour/selection_memento.h
+++ b/gtk2_ardour/selection_memento.h
@@ -16,8 +16,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_gtk_selection_memento_h__
-#define __ardour_gtk_selection_memento_h__
+#pragma once
 
 #include "pbd/statefuldestructible.h"
 
@@ -30,4 +29,3 @@ public:
 	XMLNode& get_state () const;
 	int set_state (const XMLNode&, int version);
 };
-#endif /* __ardour_gtk_selection_memento_h__ */
diff --git a/gtk2_ardour/selection_properties_box.h b/gtk2_ardour/selection_properties_box.h
index fd6ccc6dbf..447eabb4a6 100644
--- a/gtk2_ardour/selection_properties_box.h
+++ b/gtk2_ardour/selection_properties_box.h
@@ -17,8 +17,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __selection_properties_box_h__
-#define __selection_properties_box_h__
+#pragma once
 
 #include <map>
 
@@ -80,4 +79,3 @@ private:
 	void track_mouse_mode ();
 };
 
-#endif /* __selection_properties_box_h__ */
diff --git a/gtk2_ardour/selection_templates.h b/gtk2_ardour/selection_templates.h
index b48e75b9f2..b241e8cf65 100644
--- a/gtk2_ardour/selection_templates.h
+++ b/gtk2_ardour/selection_templates.h
@@ -17,8 +17,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_gtk_selection_templates_h__
-#define __ardour_gtk_selection_templates_h__
+#pragma once
 
 /* these inlines require knowledge of Region and Route classes,
    and so they are in a separate header file from selection.h to
@@ -64,4 +63,3 @@ Selection::foreach_region (void (ARDOUR::Region::*method)(A), A arg) {
 	}
 }
 
-#endif /* __ardour_gtk_selection_templates_h__ */
diff --git a/gtk2_ardour/send_ui.h b/gtk2_ardour/send_ui.h
index bf29179c84..d879a639cb 100644
--- a/gtk2_ardour/send_ui.h
+++ b/gtk2_ardour/send_ui.h
@@ -19,8 +19,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_gtk_send_ui_h__
-#define __ardour_gtk_send_ui_h__
+#pragma once
 
 #include "widgets/ardour_button.h"
 
@@ -71,4 +70,3 @@ private:
 	SendUI _ui;
 };
 
-#endif /* __ardour_gtk_send_ui_h__ */
diff --git a/gtk2_ardour/session_archive_dialog.h b/gtk2_ardour/session_archive_dialog.h
index eeef63d335..639752569a 100644
--- a/gtk2_ardour/session_archive_dialog.h
+++ b/gtk2_ardour/session_archive_dialog.h
@@ -16,8 +16,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef _gtkardour_session_archive_dialog_h_
-#define _gtkardour_session_archive_dialog_h_
+#pragma once
 
 #include <gtkmm/checkbutton.h>
 #include <gtkmm/comboboxtext.h>
@@ -65,4 +64,3 @@ private:
 	void update_progress_gui (float);
 };
 
-#endif /* __ardour_gtk_tempo_dialog_h__ */
diff --git a/gtk2_ardour/session_import_dialog.h b/gtk2_ardour/session_import_dialog.h
index 283049c168..5bee250b45 100644
--- a/gtk2_ardour/session_import_dialog.h
+++ b/gtk2_ardour/session_import_dialog.h
@@ -19,8 +19,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __session_import_dialog_h__
-#define __session_import_dialog_h__
+#pragma once
 
 #include <string>
 #include <list>
@@ -106,4 +105,3 @@ private:
 	PBD::ScopedConnectionList connections;
 };
 
-#endif
diff --git a/gtk2_ardour/session_metadata_dialog.h b/gtk2_ardour/session_metadata_dialog.h
index fa1356eec1..96e0906c50 100644
--- a/gtk2_ardour/session_metadata_dialog.h
+++ b/gtk2_ardour/session_metadata_dialog.h
@@ -20,8 +20,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __session_metadata_dialog_h__
-#define __session_metadata_dialog_h__
+#pragma once
 
 #include <memory>
 
@@ -343,4 +342,3 @@ class SessionMetadataImporter : public SessionMetadataDialog<SessionMetadataSetI
 
 };
 
-#endif
diff --git a/gtk2_ardour/session_option_editor.h b/gtk2_ardour/session_option_editor.h
index 162fbac8cf..da06dffde4 100644
--- a/gtk2_ardour/session_option_editor.h
+++ b/gtk2_ardour/session_option_editor.h
@@ -18,8 +18,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_session_option_editor_h__
-#define __gtk_ardour_session_option_editor_h__
+#pragma once
 
 #include "option_editor.h"
 
@@ -45,4 +44,3 @@ private:
 	void save_defaults ();
 };
 
-#endif /* __gtk_ardour_session_option_editor_h__ */
diff --git a/gtk2_ardour/sfdb_freesound_mootcher.h b/gtk2_ardour/sfdb_freesound_mootcher.h
index 6d52436607..ca534fdba8 100644
--- a/gtk2_ardour/sfdb_freesound_mootcher.h
+++ b/gtk2_ardour/sfdb_freesound_mootcher.h
@@ -34,8 +34,7 @@
 
 *****************************************************************************/
 
-#ifndef __gtk_ardour_sfdb_freesound_mootcher_h__
-#define __gtk_ardour_sfdb_freesound_mootcher_h__
+#pragma once
 
 #include <string>
 #include <stdio.h>
@@ -131,4 +130,3 @@ private:
 	struct curl_slist *custom_headers;
 };
 
-#endif // __gtk_ardour_sfdb_freesound_mootcher_h__
diff --git a/gtk2_ardour/sfdb_ui.h b/gtk2_ardour/sfdb_ui.h
index e93d539d31..1d489ccd97 100644
--- a/gtk2_ardour/sfdb_ui.h
+++ b/gtk2_ardour/sfdb_ui.h
@@ -22,8 +22,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_sfdb_ui_h__
-#define __ardour_sfdb_ui_h__
+#pragma once
 
 #include <string>
 #include <vector>
@@ -362,4 +361,3 @@ private:
 	bool _reset_post_import;
 };
 
-#endif // __ardour_sfdb_ui_h__
diff --git a/gtk2_ardour/slot_properties_box.h b/gtk2_ardour/slot_properties_box.h
index 4f608b539d..3367d85ae2 100644
--- a/gtk2_ardour/slot_properties_box.h
+++ b/gtk2_ardour/slot_properties_box.h
@@ -17,8 +17,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __slot_properties_box_h__
-#define __slot_properties_box_h__
+#pragma once
 
 #include <map>
 
@@ -183,4 +182,3 @@ class SlotPropertyWindow : public Gtk::Window
 	ClipEditorBox *_trim_box;
 	MidiCueEditor* _midi_editor;
 };
-#endif /* __multi_region_properties_box_h__ */
diff --git a/gtk2_ardour/soundcloud_export_selector.h b/gtk2_ardour/soundcloud_export_selector.h
index 322bd94d1e..78688d17dd 100644
--- a/gtk2_ardour/soundcloud_export_selector.h
+++ b/gtk2_ardour/soundcloud_export_selector.h
@@ -3,8 +3,7 @@
 	Adapted for Ardour by Ben Loftis, March 2012
 
 *****************************************************************************/
-#ifndef __soundcloud_export_selector_h__
-#define __soundcloud_export_selector_h__
+#pragma once
 
 #include <string>
 #include <stdio.h>
@@ -46,4 +45,3 @@ private:
 
 };
 
-#endif // __soundcloud_export_selector_h__
diff --git a/gtk2_ardour/speaker_dialog.h b/gtk2_ardour/speaker_dialog.h
index 944054cf88..f66a6dbe6f 100644
--- a/gtk2_ardour/speaker_dialog.h
+++ b/gtk2_ardour/speaker_dialog.h
@@ -18,8 +18,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_gtk_speaker_dialog_h__
-#define __ardour_gtk_speaker_dialog_h__
+#pragma once
 
 #include <gtkmm/drawingarea.h>
 #include <gtkmm/spinbutton.h>
@@ -83,4 +82,3 @@ private:
 	void speaker_position_changed ();
 };
 
-#endif /* __ardour_gtk_speaker_dialog_h__ */
diff --git a/gtk2_ardour/splash.h b/gtk2_ardour/splash.h
index 44b44bb923..30b488486a 100644
--- a/gtk2_ardour/splash.h
+++ b/gtk2_ardour/splash.h
@@ -18,8 +18,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_gtk_splash_h__
-#define __ardour_gtk_splash_h__
+#pragma once
 
 #include <set>
 
@@ -73,4 +72,3 @@ private:
 	bool idle_after_expose ();
 };
 
-#endif /* __ardour_gtk_splash_h__ */
diff --git a/gtk2_ardour/stereo_panner.h b/gtk2_ardour/stereo_panner.h
index 33896b55fb..24091d2a6e 100644
--- a/gtk2_ardour/stereo_panner.h
+++ b/gtk2_ardour/stereo_panner.h
@@ -19,8 +19,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_stereo_panner_h__
-#define __gtk_ardour_stereo_panner_h__
+#pragma once
 
 #include "pbd/signals.h"
 #include "widgets/binding_proxy.h"
@@ -115,4 +114,3 @@ private:
 	void pannable_handler ();
 };
 
-#endif /* __gtk_ardour_stereo_panner_h__ */
diff --git a/gtk2_ardour/stereo_panner_editor.h b/gtk2_ardour/stereo_panner_editor.h
index 33367c68f0..8ed26b902e 100644
--- a/gtk2_ardour/stereo_panner_editor.h
+++ b/gtk2_ardour/stereo_panner_editor.h
@@ -16,8 +16,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_stereo_panner_editor_h__
-#define __gtk_ardour_stereo_panner_editor_h__
+#pragma once
 
 #include <gtkmm/spinbutton.h>
 #include "panner_editor.h"
@@ -46,4 +45,3 @@ private:
 	PBD::ScopedConnectionList _connections;
 };
 
-#endif // __gtk_ardour_stereo_panner_editor_h__
diff --git a/gtk2_ardour/streamview.h b/gtk2_ardour/streamview.h
index 477331cc09..d6ee5a3bde 100644
--- a/gtk2_ardour/streamview.h
+++ b/gtk2_ardour/streamview.h
@@ -22,8 +22,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_streamview_h__
-#define __ardour_streamview_h__
+#pragma once
 
 #include <list>
 #include <cmath>
@@ -198,5 +197,4 @@ protected:
 	void setup_new_rec_layer_time (std::shared_ptr<ARDOUR::Region>);
 };
 
-#endif /* __ardour_streamview_h__ */
 
diff --git a/gtk2_ardour/strip_selection.h b/gtk2_ardour/strip_selection.h
index e4f40d903a..05602fddb7 100644
--- a/gtk2_ardour/strip_selection.h
+++ b/gtk2_ardour/strip_selection.h
@@ -18,8 +18,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_gtk_strip_selection_h__
-#define __ardour_gtk_strip_selection_h__
+#pragma once
 
 #include <list>
 
@@ -27,4 +26,3 @@ class MixerStrip;
 
 struct MixerStripSelection : list<MixerStrip*> {};
 
-#endif /* __ardour_gtk_strip_selection_h__ */
diff --git a/gtk2_ardour/stripable_colorpicker.h b/gtk2_ardour/stripable_colorpicker.h
index 90166d3ade..18971d546e 100644
--- a/gtk2_ardour/stripable_colorpicker.h
+++ b/gtk2_ardour/stripable_colorpicker.h
@@ -16,8 +16,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtkardour_stripable_colorpicker_h__
-#define __gtkardour_stripable_colorpicker_h__
+#pragma once
 
 #include <memory>
 
@@ -65,4 +64,3 @@ private:
 	StripableColorDialog _color_picker;
 };
 
-#endif
diff --git a/gtk2_ardour/stripable_time_axis.h b/gtk2_ardour/stripable_time_axis.h
index ddd78f26ba..5bfe5c0052 100644
--- a/gtk2_ardour/stripable_time_axis.h
+++ b/gtk2_ardour/stripable_time_axis.h
@@ -16,8 +16,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_stripable_time_axis_h__
-#define __ardour_stripable_time_axis_h__
+#pragma once
 
 #include "automation_time_axis.h"
 #include "time_axis_view.h"
@@ -81,4 +80,3 @@ protected:
 	bool                  no_redraw;
 };
 
-#endif /* __ardour_stripable_time_axis_h__ */
diff --git a/gtk2_ardour/tempo_curve.h b/gtk2_ardour/tempo_curve.h
index fd196e0b23..a86c067db3 100644
--- a/gtk2_ardour/tempo_curve.h
+++ b/gtk2_ardour/tempo_curve.h
@@ -17,8 +17,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_tempo_curve_h__
-#define __gtk_ardour_tempo_curve_h__
+#pragma once
 
 #include <string>
 #include <glib.h>
@@ -89,4 +88,3 @@ private:
 	ArdourCanvas::Text*   _start_text;
 	ArdourCanvas::Text*   _end_text;
 };
-#endif /* __gtk_ardour_tempo_curve_h__ */
diff --git a/gtk2_ardour/tempo_dialog.h b/gtk2_ardour/tempo_dialog.h
index 9a0dbb784e..ede442b1ec 100644
--- a/gtk2_ardour/tempo_dialog.h
+++ b/gtk2_ardour/tempo_dialog.h
@@ -22,8 +22,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_gtk_tempo_dialog_h__
-#define __ardour_gtk_tempo_dialog_h__
+#pragma once
 
 #include <gtkmm/entry.h>
 #include <gtkmm/frame.h>
@@ -179,4 +178,3 @@ private:
 	Gtk::Entry   when_bar_entry;
 };
 
-#endif /* __ardour_gtk_tempo_dialog_h__ */
diff --git a/gtk2_ardour/tempo_lines.h b/gtk2_ardour/tempo_lines.h
index a8d4ea2e62..7a84f705f4 100644
--- a/gtk2_ardour/tempo_lines.h
+++ b/gtk2_ardour/tempo_lines.h
@@ -18,8 +18,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_tempo_lines_h__
-#define __ardour_tempo_lines_h__
+#pragma once
 
 #include "ardour/tempo.h"
 
@@ -50,4 +49,3 @@ private:
 	ARDOUR::BeatsSamplesConverter* _bfc;
 };
 
-#endif /* __ardour_tempo_lines_h__ */
diff --git a/gtk2_ardour/time_axis_view.h b/gtk2_ardour/time_axis_view.h
index 62b72a5e28..0b0b1b3d97 100644
--- a/gtk2_ardour/time_axis_view.h
+++ b/gtk2_ardour/time_axis_view.h
@@ -24,8 +24,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_gtk_time_axis_h__
-#define __ardour_gtk_time_axis_h__
+#pragma once
 
 #include <vector>
 #include <list>
@@ -334,4 +333,3 @@ private:
 
 }; /* class TimeAxisView */
 
-#endif /* __ardour_gtk_time_axis_h__ */
diff --git a/gtk2_ardour/time_axis_view_item.h b/gtk2_ardour/time_axis_view_item.h
index edecdacd57..192ed49cda 100644
--- a/gtk2_ardour/time_axis_view_item.h
+++ b/gtk2_ardour/time_axis_view_item.h
@@ -22,8 +22,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_time_axis_view_item_h__
-#define __gtk_ardour_time_axis_view_item_h__
+#pragma once
 
 #include <string>
 #include <gdk/gdk.h>
@@ -237,4 +236,3 @@ private:
 
 }; /* class TimeAxisViewItem */
 
-#endif /* __gtk_ardour_time_axis_view_item_h__ */
diff --git a/gtk2_ardour/time_fx_dialog.h b/gtk2_ardour/time_fx_dialog.h
index d1665e776d..a06802cedd 100644
--- a/gtk2_ardour/time_fx_dialog.h
+++ b/gtk2_ardour/time_fx_dialog.h
@@ -19,8 +19,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_time_fx_dialog_h__
-#define __ardour_time_fx_dialog_h__
+#pragma once
 
 #include <gtkmm/adjustment.h>
 #include <gtkmm/spinbutton.h>
@@ -108,4 +107,3 @@ private:
 	void timer_update ();
 };
 
-#endif /* __ardour_time_fx_dialog_h__ */
diff --git a/gtk2_ardour/time_info_box.h b/gtk2_ardour/time_info_box.h
index ce5d7c00c3..1991d2c82d 100644
--- a/gtk2_ardour/time_info_box.h
+++ b/gtk2_ardour/time_info_box.h
@@ -17,8 +17,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __time_info_box_h__
-#define __time_info_box_h__
+#pragma once
 
 #include <map>
 
@@ -79,4 +78,3 @@ private:
 	void track_mouse_mode ();
 };
 
-#endif /* __time_info_box_h__ */
diff --git a/gtk2_ardour/time_selection.h b/gtk2_ardour/time_selection.h
index 154b2dfd13..87540c71c2 100644
--- a/gtk2_ardour/time_selection.h
+++ b/gtk2_ardour/time_selection.h
@@ -17,8 +17,7 @@
 
 */
 
-#ifndef __ardour_gtk_time_selection_h__
-#define __ardour_gtk_time_selection_h__
+#pragma once
 
 #include <list>
 #include "ardour/types.h"
@@ -46,4 +45,3 @@ public:
 };
 
 
-#endif /* __ardour_gtk_time_selection_h__ */
diff --git a/gtk2_ardour/track_selection.h b/gtk2_ardour/track_selection.h
index 97ed46cf19..80ae86919e 100644
--- a/gtk2_ardour/track_selection.h
+++ b/gtk2_ardour/track_selection.h
@@ -18,8 +18,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_gtk_track_selection_h__
-#define __ardour_gtk_track_selection_h__
+#pragma once
 
 #include "track_view_list.h"
 
@@ -30,4 +29,3 @@ public:
 	TrackSelection (TrackViewList const &);
 };
 
-#endif /* __ardour_gtk_track_selection_h__ */
diff --git a/gtk2_ardour/track_view_list.h b/gtk2_ardour/track_view_list.h
index 8874795703..31364118bf 100644
--- a/gtk2_ardour/track_view_list.h
+++ b/gtk2_ardour/track_view_list.h
@@ -17,8 +17,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_gtk_track_view_list_h__
-#define __ardour_gtk_track_view_list_h__
+#pragma once
 
 #include "ardour/types.h" /* XXX is this here because of some Cocoa nonsense ? */
 
@@ -119,5 +118,4 @@ public:
 	}
 };
 
-#endif
 
diff --git a/gtk2_ardour/transcode_ffmpeg.h b/gtk2_ardour/transcode_ffmpeg.h
index 372d722c3d..725428b511 100644
--- a/gtk2_ardour/transcode_ffmpeg.h
+++ b/gtk2_ardour/transcode_ffmpeg.h
@@ -15,8 +15,7 @@
  * with this program; if not, write to the Free Software Foundation, Inc.,
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
-#ifndef __ardour_transcode_ffmpeg_h__
-#define __ardour_transcode_ffmpeg_h__
+#pragma once
 
 #include <string>
 
@@ -203,4 +202,3 @@ protected:
 	bool                debug_enable;
 };
 
-#endif /* __ardour_transcode_ffmpeg_h__ */
diff --git a/gtk2_ardour/transcode_video_dialog.h b/gtk2_ardour/transcode_video_dialog.h
index b4efdb44d9..47d75ae1b9 100644
--- a/gtk2_ardour/transcode_video_dialog.h
+++ b/gtk2_ardour/transcode_video_dialog.h
@@ -15,8 +15,7 @@
  * with this program; if not, write to the Free Software Foundation, Inc.,
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
-#ifndef __gtk_ardour_transcode_video_dialog_h__
-#define __gtk_ardour_transcode_video_dialog_h__
+#pragma once
 
 #include <string>
 
@@ -126,4 +125,3 @@ private:
 	Gtk::CheckButton  debug_checkbox;
 };
 
-#endif /* __gtk_ardour_transcode_video_dialog_h__ */
diff --git a/gtk2_ardour/transform_dialog.h b/gtk2_ardour/transform_dialog.h
index f53304f3e8..d86e387d2c 100644
--- a/gtk2_ardour/transform_dialog.h
+++ b/gtk2_ardour/transform_dialog.h
@@ -16,8 +16,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __transform_dialog_h__
-#define __transform_dialog_h__
+#pragma once
 
 #include <list>
 #include <string>
@@ -138,4 +137,3 @@ private:
 	Gtk::Button   _add_button;
 };
 
-#endif /* __transform_dialog_h__ */
diff --git a/gtk2_ardour/transport_masters_dialog.h b/gtk2_ardour/transport_masters_dialog.h
index caf756969b..0a1e39141e 100644
--- a/gtk2_ardour/transport_masters_dialog.h
+++ b/gtk2_ardour/transport_masters_dialog.h
@@ -16,8 +16,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_gtk_transport_masters_dialog_h__
-#define __ardour_gtk_transport_masters_dialog_h__
+#pragma once
 
 #include <vector>
 #include <string>
@@ -198,4 +197,3 @@ class TransportMastersWindow : public ArdourWindow
 };
 
 
-#endif /* __ardour_gtk_transport_masters_dialog_h__ */
diff --git a/gtk2_ardour/transpose_dialog.h b/gtk2_ardour/transpose_dialog.h
index a6f86dd729..0e1eb7d61a 100644
--- a/gtk2_ardour/transpose_dialog.h
+++ b/gtk2_ardour/transpose_dialog.h
@@ -16,8 +16,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_transpose_dialog_h__
-#define __ardour_transpose_dialog_h__
+#pragma once
 
 #include <gtkmm/spinbutton.h>
 #include "ardour_dialog.h"
@@ -42,4 +41,3 @@ private:
 	Gtk::SpinButton _semitones_spinner;
 };
 
-#endif /* __ardour_transpose_dialog_h__ */
diff --git a/gtk2_ardour/trigger_clip_picker.h b/gtk2_ardour/trigger_clip_picker.h
index ab9bb2604b..46b136c54a 100644
--- a/gtk2_ardour/trigger_clip_picker.h
+++ b/gtk2_ardour/trigger_clip_picker.h
@@ -16,8 +16,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_trigger_clip_picker_h__
-#define __gtk_ardour_trigger_clip_picker_h__
+#pragma once
 
 #include <set>
 #include <string>
@@ -154,4 +153,3 @@ private:
 	sigc::connection          _idle_connection;
 };
 
-#endif
diff --git a/gtk2_ardour/trigger_page.h b/gtk2_ardour/trigger_page.h
index ae2117cb2d..4eff24fc74 100644
--- a/gtk2_ardour/trigger_page.h
+++ b/gtk2_ardour/trigger_page.h
@@ -16,8 +16,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_trigger_page_h__
-#define __gtk_ardour_trigger_page_h__
+#pragma once
 
 #include <gtkmm/box.h>
 
@@ -142,4 +141,3 @@ private:
 	sigc::connection         _fast_screen_update_connection;
 };
 
-#endif /* __gtk_ardour_trigger_page_h__ */
diff --git a/gtk2_ardour/trigger_selection.h b/gtk2_ardour/trigger_selection.h
index 76db837aee..46971aa494 100644
--- a/gtk2_ardour/trigger_selection.h
+++ b/gtk2_ardour/trigger_selection.h
@@ -17,8 +17,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_gtk_trigger_selection_h__
-#define __ardour_gtk_trigger_selection_h__
+#pragma once
 
 #include <list>
 
@@ -29,4 +28,3 @@ class TriggerSelection : public std::list<TriggerEntry*>
    public:
 };
 
-#endif /* __ardour_gtk_trigger_selection_h__ */
diff --git a/gtk2_ardour/trigger_ui.h b/gtk2_ardour/trigger_ui.h
index 2f78ba5379..43b8787ad1 100644
--- a/gtk2_ardour/trigger_ui.h
+++ b/gtk2_ardour/trigger_ui.h
@@ -16,8 +16,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_gtk_trigger_ui_h__
-#define __ardour_gtk_trigger_ui_h__
+#pragma once
 
 #include "gtkmm/colorselection.h"
 #include "gtkmm/entry.h"
@@ -133,4 +132,3 @@ protected:
 
 
 
-#endif /* __ardour_gtk_trigger_ui_h__ */
diff --git a/gtk2_ardour/ui_config.h b/gtk2_ardour/ui_config.h
index 9fb71d015c..8a1da7b10d 100644
--- a/gtk2_ardour/ui_config.h
+++ b/gtk2_ardour/ui_config.h
@@ -21,8 +21,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_ui_configuration_h__
-#define __ardour_ui_configuration_h__
+#pragma once
 
 #include <sstream>
 #include <ostream>
@@ -155,4 +154,3 @@ private:
 	uint32_t block_save;
 };
 
-#endif /* __ardour_ui_configuration_h__ */
diff --git a/gtk2_ardour/utils.h b/gtk2_ardour/utils.h
index 714478ee4e..d523c52827 100644
--- a/gtk2_ardour/utils.h
+++ b/gtk2_ardour/utils.h
@@ -26,8 +26,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_gtk_utils_h__
-#define __ardour_gtk_utils_h__
+#pragma once
 
 #include <string>
 #include <cmath>
@@ -123,4 +122,3 @@ bool convert_drop_to_paths (std::vector<std::string>&, const Gtk::SelectionData&
 void format_position (ARDOUR::Session*, Temporal::timepos_t const& pos, char* buf, size_t bufsize, bool onoff = true);
 
 } // namespace
-#endif /* __ardour_gtk_utils_h__ */
diff --git a/gtk2_ardour/utils_videotl.h b/gtk2_ardour/utils_videotl.h
index d62c7bdd37..94c29bc1b8 100644
--- a/gtk2_ardour/utils_videotl.h
+++ b/gtk2_ardour/utils_videotl.h
@@ -19,8 +19,7 @@
  *  @brief common functions used for video-file im/export
  */
 
-#ifndef __gtk_ardour_video_utils_h__
-#define __gtk_ardour_video_utils_h__
+#pragma once
 
 #include <string>
 
@@ -55,4 +54,3 @@ bool video_query_info (
 		);
 };
 
-#endif /* __gtk_ardour_video_utils_h__ */
diff --git a/gtk2_ardour/vca_time_axis.h b/gtk2_ardour/vca_time_axis.h
index 8863140b01..0f2ede507f 100644
--- a/gtk2_ardour/vca_time_axis.h
+++ b/gtk2_ardour/vca_time_axis.h
@@ -17,8 +17,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_vca_time_axis_h__
-#define __ardour_vca_time_axis_h__
+#pragma once
 
 #include "widgets/ardour_button.h"
 
@@ -101,4 +100,3 @@ private:
 	StripableColorDialog _color_picker;
 };
 
-#endif /* __ardour_vca_time_axis_h__ */
diff --git a/gtk2_ardour/velocity_display.h b/gtk2_ardour/velocity_display.h
index 1150067513..f16694532e 100644
--- a/gtk2_ardour/velocity_display.h
+++ b/gtk2_ardour/velocity_display.h
@@ -18,8 +18,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_velocity_display_h__
-#define __gtk_ardour_velocity_display_h__
+#pragma once
 
 #include "canvas/rectangle.h"
 #include "canvas/poly_line.h"
@@ -99,4 +98,3 @@ class VelocityDisplay
 	void sensitize_lollis ();
 };
 
-#endif /* __gtk_ardour_velocity_display_h__ */
diff --git a/gtk2_ardour/velocity_ghost_region.h b/gtk2_ardour/velocity_ghost_region.h
index e94f8879cf..8b64da032e 100644
--- a/gtk2_ardour/velocity_ghost_region.h
+++ b/gtk2_ardour/velocity_ghost_region.h
@@ -18,8 +18,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_velocity_region_view_h__
-#define __gtk_ardour_velocity_region_view_h__
+#pragma once
 
 #include "canvas/poly_line.h"
 
@@ -53,4 +52,3 @@ class VelocityGhostRegion : public MidiGhostRegion, public VelocityDisplay
 	bool lollevent (GdkEvent*, GhostEvent*);
 };
 
-#endif /* __gtk_ardour_velocity_region_view_h__ */
diff --git a/gtk2_ardour/verbose_cursor.h b/gtk2_ardour/verbose_cursor.h
index ecbe8f3984..7579f0b752 100644
--- a/gtk2_ardour/verbose_cursor.h
+++ b/gtk2_ardour/verbose_cursor.h
@@ -17,8 +17,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __gtk_ardour_verbose_cursor_h__
-#define __gtk_ardour_verbose_cursor_h__
+#pragma once
 
 #include "ardour/types.h"
 #include "canvas/canvas.h"
@@ -52,4 +51,3 @@ private:
 	void color_handler ();
 };
 
-#endif // __gtk_ardour_verbose_cursor_h__
diff --git a/gtk2_ardour/video_image_frame.h b/gtk2_ardour/video_image_frame.h
index ae7a9aa3a1..c2792b6ae7 100644
--- a/gtk2_ardour/video_image_frame.h
+++ b/gtk2_ardour/video_image_frame.h
@@ -16,8 +16,7 @@
  * with this program; if not, write to the Free Software Foundation, Inc.,
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
-#ifndef __ardour_video_image_frame_h__
-#define __ardour_video_image_frame_h__
+#pragma once
 
 #include <string>
 #include <glib.h>
@@ -104,4 +103,3 @@ class VideoImageFrame : public sigc::trackable
 
 };
 
-#endif /* __ardour_video_image_frame_h__ */
diff --git a/gtk2_ardour/video_monitor.h b/gtk2_ardour/video_monitor.h
index a122e2cacf..d999b0aaad 100644
--- a/gtk2_ardour/video_monitor.h
+++ b/gtk2_ardour/video_monitor.h
@@ -15,8 +15,7 @@
  * with this program; if not, write to the Free Software Foundation, Inc.,
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
-#ifndef __ardour_video_monitor_h__
-#define __ardour_video_monitor_h__
+#pragma once
 
 #include <string>
 
@@ -112,4 +111,3 @@ class VideoMonitor : public sigc::trackable , public ARDOUR::SessionHandlePtr, p
 #endif
 };
 
-#endif /* __ardour_video_monitor_h__ */
diff --git a/gtk2_ardour/video_server_dialog.h b/gtk2_ardour/video_server_dialog.h
index 7f27fa9bbd..2b0a4ed149 100644
--- a/gtk2_ardour/video_server_dialog.h
+++ b/gtk2_ardour/video_server_dialog.h
@@ -15,8 +15,7 @@
  * with this program; if not, write to the Free Software Foundation, Inc.,
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
-#ifndef __gtk_ardour_video_server_dialog_h__
-#define __gtk_ardour_video_server_dialog_h__
+#pragma once
 
 #include <string>
 
@@ -69,4 +68,3 @@ private:
 	Gtk::CheckButton  showagain_checkbox;
 };
 
-#endif /* __gtk_ardour_video_server_dialog_h__ */
diff --git a/gtk2_ardour/video_timeline.h b/gtk2_ardour/video_timeline.h
index 3b7b7f882d..d6dfa516be 100644
--- a/gtk2_ardour/video_timeline.h
+++ b/gtk2_ardour/video_timeline.h
@@ -16,8 +16,7 @@
  * with this program; if not, write to the Free Software Foundation, Inc.,
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
-#ifndef __ardour_video_timeline_h__
-#define __ardour_video_timeline_h__
+#pragma once
 
 #include <string>
 
@@ -149,4 +148,3 @@ class VideoTimeLine : public sigc::trackable, public ARDOUR::SessionHandlePtr, p
 	PBD::ScopedConnection sessionsave;
 };
 
-#endif /* __ardour_video_timeline_h__ */
diff --git a/gtk2_ardour/vst_plugin_ui.h b/gtk2_ardour/vst_plugin_ui.h
index fb0a5b649f..222e6aa254 100644
--- a/gtk2_ardour/vst_plugin_ui.h
+++ b/gtk2_ardour/vst_plugin_ui.h
@@ -16,8 +16,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __ardour_vst_plugin_ui_h__
-#define __ardour_vst_plugin_ui_h__
+#pragma once
 
 #include "plugin_ui.h"
 
@@ -57,4 +56,3 @@ private:
 	void preset_selected (ARDOUR::Plugin::PresetRecord preset);
 };
 
-#endif
diff --git a/gtk2_ardour/windows_vst_plugin_ui.h b/gtk2_ardour/windows_vst_plugin_ui.h
index 73fc0a87ab..b42c33ce60 100644
--- a/gtk2_ardour/windows_vst_plugin_ui.h
+++ b/gtk2_ardour/windows_vst_plugin_ui.h
@@ -17,8 +17,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef __windows_vst_plugin_ui_h__
-#define __windows_vst_plugin_ui_h__
+#pragma once
 
 #include "pbd/signals.h"
 #include "vst_plugin_ui.h"