initial data structure for musical scales (derived from mode)

This is built around a MIDI-like assumption that we have a fixed (integer) number of
note IDs and a semitone between them. We will need to expand this definition in the
future to handle Bohlen-Pierce, maqams and various other non-12TET scale systems

libs/ardour/ardour/scale.h

@@ -0,0 +1,38 @@
+/*
+ * Copyright (C) 2021 Paul Davis <paul@linuxaudiosystems.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#ifndef __ardour_scale_h__
+#define __ardour_scale_h__
+
+#include "ardour/mode.h"
+
+class MusicalScale : MusicalMode
+{
+  public:
+	MusicalScale (Type t, int root) : MusicalMode (t), _root (root) {}
+	~MusicalScale ();
+
+	int root () const { return _root; }
+	void set_root (int);
+
+  private:
+	int _root;
+
+};
+
+#endif /* __ardour_scale_h__ */

libs/ardour/scale.cc

@@ -0,0 +1,26 @@
+/*
+ * Copyright (C) 2021 Paul Davis <paul@linuxaudiosystems.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include "ardour/scale.h"
+
+void
+MusicalScale::set_root (int r)
+{
+	_root = r;
+}
+

libs/ardour/wscript

@@ -206,7 +206,8 @@ libardour_sources = [
         'route_group_member.cc',
         'rb_effect.cc',
         'rt_tasklist.cc',
-        'scene_change.cc',
+        'scale.cc',
+	'scene_change.cc',
         'search_paths.cc',
         'selection.cc',
         'send.cc',