diff --git a/libs/ardour/ardour/audioregion.h b/libs/ardour/ardour/audioregion.h
index e11eaa439c..f28296d81e 100644
--- a/libs/ardour/ardour/audioregion.h
+++ b/libs/ardour/ardour/audioregion.h
@@ -161,12 +161,12 @@ class LIBARDOUR_API AudioRegion : public Region, public AudioReadable
 	/* automation */
 
 	std::shared_ptr<Evoral::Control>
-	control(const Evoral::Parameter& id, bool create=false) {
+		control(const Evoral::Parameter& id, bool create=false) {
 		return _automatable.control(id, create);
 	}
 
 	virtual std::shared_ptr<const Evoral::Control>
-	control(const Evoral::Parameter& id) const {
+		control(const Evoral::Parameter& id) const {
 		return _automatable.control(id);
 	}
 
diff --git a/libs/ardour/ardour/automatable.h b/libs/ardour/ardour/automatable.h
index 55a4270c19..0e40021b67 100644
--- a/libs/ardour/ardour/automatable.h
+++ b/libs/ardour/ardour/automatable.h
@@ -34,6 +34,7 @@
 
 #include "evoral/ControlSet.h"
 
+#include "temporal/domain_swap.h"
 #include "temporal/domain_provider.h"
 
 #include "ardour/libardour_visibility.h"
@@ -50,7 +51,7 @@ class AutomationControl;
 /* The inherited ControlSet is virtual because AutomatableSequence inherits
  * from this AND EvoralSequence, which is also a ControlSet
  */
-class LIBARDOUR_API Automatable : virtual public Evoral::ControlSet, public Slavable, public Temporal::TimeDomainProvider
+class LIBARDOUR_API Automatable : virtual public Evoral::ControlSet, public Slavable, public Temporal::TimeDomainProvider, public Temporal::TimeDomainSwapper
 {
 public:
 	Automatable(Session&, Temporal::TimeDomainProvider const &);
@@ -119,6 +120,9 @@ public:
 
 	PBD::Signal0<void> AutomationStateChanged;
 
+	void start_domain_bounce (Temporal::DomainBounceInfo&);
+	void finish_domain_bounce (Temporal::DomainBounceInfo&);
+
 protected:
 	Session& _a_session;
 
diff --git a/libs/ardour/ardour/location.h b/libs/ardour/ardour/location.h
index 9ec902c175..a5f1190c2c 100644
--- a/libs/ardour/ardour/location.h
+++ b/libs/ardour/ardour/location.h
@@ -38,6 +38,8 @@
 #include "pbd/stateful.h"
 #include "pbd/statefuldestructible.h"
 
+#include "temporal/domain_provider.h"
+#include "temporal/domain_swap.h"
 #include "temporal/types.h"
 
 #include "ardour/ardour.h"
@@ -173,8 +175,12 @@ public:
 
 	Temporal::TimeDomain position_time_domain() const { return _start.time_domain(); }
 
-	void globally_change_time_domain (Temporal::TimeDomain from, Temporal::TimeDomain to);
-	void change_time_domain (Temporal::TimeDomain from, Temporal::TimeDomain to);
+	/* Similar to, but not identical to the Temporal::TimeDomainSwapper API */
+
+	void start_domain_bounce (Temporal::DomainBounceInfo&);
+	void finish_domain_bounce (Temporal::DomainBounceInfo&);
+
+	void set_time_domain (Temporal::TimeDomain);
 
 	class ChangeSuspender {
 		public:
@@ -209,7 +215,7 @@ private:
 		Lock,
 		Cue,
 		Scene,
-		Domain
+		Domain,
 	};
 
 	void emit_signal (Signal);
@@ -233,7 +239,7 @@ private:
 };
 
 /** A collection of session locations including unique dedicated locations (loop, punch, etc) */
-class LIBARDOUR_API Locations : public SessionHandleRef, public PBD::StatefulDestructible
+class LIBARDOUR_API Locations : public SessionHandleRef, public PBD::StatefulDestructible, public Temporal::TimeDomainProvider, public Temporal::TimeDomainSwapper
 {
 public:
 	typedef std::list<Location *> LocationList;
@@ -303,8 +309,11 @@ public:
 
 	void find_all_between (timepos_t const & start, timepos_t const & end, LocationList&, Location::Flags);
 
-	void globally_change_time_domain (Temporal::TimeDomain from, Temporal::TimeDomain to);
-	void change_time_domain (Temporal::TimeDomain from, Temporal::TimeDomain to);
+	void set_time_domain (Temporal::TimeDomain);
+	void start_domain_bounce (Temporal::DomainBounceInfo&);
+	void finish_domain_bounce (Temporal::DomainBounceInfo&);
+
+	void time_domain_changed ();
 
 	PBD::Signal1<void,Location*> current_changed;
 
diff --git a/libs/ardour/ardour/midi_region.h b/libs/ardour/ardour/midi_region.h
index c6d9621b34..b61f49950a 100644
--- a/libs/ardour/ardour/midi_region.h
+++ b/libs/ardour/ardour/midi_region.h
@@ -26,7 +26,6 @@
 #include <vector>
 
 #include "temporal/beats.h"
-#include "temporal/domainswap.h"
 #include "temporal/range.h"
 
 #include "pbd/string_convert.h"
@@ -55,7 +54,7 @@ class ThawList;
 
 template<typename T> class MidiRingBuffer;
 
-class LIBARDOUR_API MidiRegion : public Region, public Temporal::TimeDomainSwapper
+class LIBARDOUR_API MidiRegion : public Region
 {
   public:
 	~MidiRegion();
@@ -117,8 +116,8 @@ class LIBARDOUR_API MidiRegion : public Region, public Temporal::TimeDomainSwapp
 	                  timecnt_t const &               read_length,
 	                  MidiChannelFilter*              filter) const;
 
-	void globally_change_time_domain (Temporal::TimeDomain from, Temporal::TimeDomain to);
-	void swap_domain (Temporal::TimeDomain, Temporal::TimeDomain);
+	void start_domain_bounce (Temporal::DomainBounceInfo&);
+	void finish_domain_bounce (Temporal::DomainBounceInfo&);
 
   protected:
 
diff --git a/libs/ardour/ardour/pannable.h b/libs/ardour/ardour/pannable.h
index 1179b95994..1c3253fbec 100644
--- a/libs/ardour/ardour/pannable.h
+++ b/libs/ardour/ardour/pannable.h
@@ -76,6 +76,9 @@ public:
 
 	bool has_state() const { return _has_state; }
 
+	void start_domain_bounce (Temporal::DomainBounceInfo&);
+	void finish_domain_bounce (Temporal::DomainBounceInfo&);
+
 protected:
 	virtual XMLNode& state () const;
 
diff --git a/libs/ardour/ardour/playlist.h b/libs/ardour/ardour/playlist.h
index c56f014117..ed4ca9e0c9 100644
--- a/libs/ardour/ardour/playlist.h
+++ b/libs/ardour/ardour/playlist.h
@@ -301,7 +301,8 @@ public:
 	void set_capture_insertion_in_progress (bool yn);
 
 	void time_domain_changed ();
-	void globally_change_time_domain (Temporal::TimeDomain from, Temporal::TimeDomain to);
+	void start_domain_bounce (Temporal::DomainBounceInfo&);
+	void finish_domain_bounce (Temporal::DomainBounceInfo&);
 
 protected:
 	friend class Session;
diff --git a/libs/ardour/ardour/region.h b/libs/ardour/ardour/region.h
index aa1416138b..00e575ce9a 100644
--- a/libs/ardour/ardour/region.h
+++ b/libs/ardour/ardour/region.h
@@ -29,6 +29,7 @@
 
 #include <boost/utility.hpp>
 
+#include "temporal/domain_swap.h"
 #include "temporal/timeline.h"
 #include "temporal/range.h"
 
@@ -96,6 +97,7 @@ class LIBARDOUR_API Region
 	, public std::enable_shared_from_this<Region>
 	, public Trimmable
 	, public Movable
+	, public Temporal::TimeDomainSwapper
 {
 public:
 	typedef std::vector<std::shared_ptr<Source> > SourceList;
@@ -115,8 +117,8 @@ public:
 
 	const DataType& data_type () const { return _type; }
 	Temporal::TimeDomain time_domain() const;
-	virtual void globally_change_time_domain (Temporal::TimeDomain from, Temporal::TimeDomain to);
-	virtual void change_time_domain (Temporal::TimeDomain from, Temporal::TimeDomain to);
+	void start_domain_bounce (Temporal::DomainBounceInfo&);
+	void finish_domain_bounce (Temporal::DomainBounceInfo&);
 
 	/** How the region parameters play together:
 	 *
@@ -386,7 +388,7 @@ public:
 	/* automation */
 
 	virtual std::shared_ptr<Evoral::Control>
-	control (const Evoral::Parameter& id, bool create=false) = 0;
+		control (const Evoral::Parameter& id, bool create=false) = 0;
 
 	virtual std::shared_ptr<const Evoral::Control>
 	control (const Evoral::Parameter& id) const = 0;
diff --git a/libs/ardour/ardour/route.h b/libs/ardour/ardour/route.h
index c7450f8f67..aad8930af4 100644
--- a/libs/ardour/ardour/route.h
+++ b/libs/ardour/ardour/route.h
@@ -41,6 +41,7 @@
 #include "pbd/controllable.h"
 #include "pbd/destructible.h"
 
+#include "temporal/domain_swap.h"
 #include "temporal/types.h"
 
 #include "ardour/ardour.h"
@@ -612,7 +613,6 @@ public:
 
 	virtual void use_captured_sources (SourceList& srcs, CaptureInfos const &) {}
 
-	void globally_change_time_domain (Temporal::TimeDomain from, Temporal::TimeDomain to);
 
 protected:
 	friend class Session;
diff --git a/libs/ardour/ardour/session.h b/libs/ardour/ardour/session.h
index 21eae1975e..8eaf7672e4 100644
--- a/libs/ardour/ardour/session.h
+++ b/libs/ardour/ardour/session.h
@@ -1387,7 +1387,8 @@ public:
 	bool bang_trigger_at(int32_t route_index, int32_t row_index);
 	bool unbang_trigger_at(int32_t route_index, int32_t row_index);
 
-	PBD::Command* globally_change_time_domain (Temporal::TimeDomain from, Temporal::TimeDomain to);
+	void start_domain_bounce (Temporal::DomainBounceInfo&);
+	void finish_domain_bounce (Temporal::DomainBounceInfo&);
 
 protected:
 	friend class AudioEngine;
diff --git a/libs/ardour/ardour/session_playlists.h b/libs/ardour/ardour/session_playlists.h
index 242c78c2c0..b68435436a 100644
--- a/libs/ardour/ardour/session_playlists.h
+++ b/libs/ardour/ardour/session_playlists.h
@@ -70,7 +70,8 @@ public:
 	std::vector<std::shared_ptr<Playlist> > get_unused () const;
 	uint32_t n_playlists() const;
 
-	void globally_change_time_domain (Temporal::TimeDomain from, Temporal::TimeDomain to);
+	void start_domain_bounce (Temporal::DomainBounceInfo&);
+	void finish_domain_bounce (Temporal::DomainBounceInfo&);
 
 private:
 	friend class Session;
diff --git a/libs/ardour/automatable.cc b/libs/ardour/automatable.cc
index 3fe3b0129d..952b44503b 100644
--- a/libs/ardour/automatable.cc
+++ b/libs/ardour/automatable.cc
@@ -743,3 +743,13 @@ Automatable::find_prev_ac_event (std::shared_ptr<AutomationControl> c, timepos_t
 		++i;
 	}
 }
+
+void
+Automatable::start_domain_bounce (Temporal::DomainBounceInfo& cmd)
+{
+}
+
+void
+Automatable::finish_domain_bounce (Temporal::DomainBounceInfo& cmd)
+{
+}
diff --git a/libs/ardour/location.cc b/libs/ardour/location.cc
index 8b2017ac9e..b7a1ec4591 100644
--- a/libs/ardour/location.cc
+++ b/libs/ardour/location.cc
@@ -92,22 +92,8 @@ Location::Location (Session& s, timepos_t const & start, timepos_t const & end,
 	set_position_time_domain (_session.time_domain());
 }
 
-void
-Location::set_position_time_domain (TimeDomain domain)
-{
-	if (_start.time_domain() == domain) {
-		return;
-	}
-
-	_start.set_time_domain (domain);
-	_end.set_time_domain (domain);
-
-	emit_signal (Domain); /* EMIT SIGNAL */
-}
-
 Location::Location (const Location& other)
 	: SessionHandleRef (other._session)
-	, StatefulDestructible()
 	, _name (other._name)
 	, _start (other._start)
 	, _end (other._end)
@@ -253,6 +239,26 @@ Location::actually_emit_signal (Signal s)
 	}
 }
 
+
+void
+Location::set_position_time_domain (TimeDomain domain)
+{
+	if (_start.time_domain() == domain) {
+		return;
+	}
+
+	_start.set_time_domain (domain);
+	_end.set_time_domain (domain);
+
+	// emit_signal (Domain); /* EMIT SIGNAL */
+}
+
+void
+Location::set_time_domain (TimeDomain domain)
+{
+	set_position_time_domain (domain);
+}
+
 /** Set location name */
 void
 Location::set_name (const std::string& str)
@@ -777,32 +783,53 @@ Location::set_scene_change (std::shared_ptr<SceneChange>  sc)
 }
 
 void
-Location::globally_change_time_domain (Temporal::TimeDomain from, Temporal::TimeDomain to)
+Location::start_domain_bounce (Temporal::DomainBounceInfo& cmd)
 {
-	assert (domain_swap);
-
-	if (_start.time_domain() == from) {
-
-		_start.set_time_domain (to);
-		_end.set_time_domain (to);
-
-		domain_swap->add (_start);
-		domain_swap->add (_end);
+	if (_start.time_domain() == cmd.to) {
+		/* has the right domain to begin with */
+		return;
 	}
+
+	timepos_t s (_start);
+	timepos_t e (_end);
+
+	s.set_time_domain (cmd.to);
+	e.set_time_domain (cmd.to);
+
+	cmd.positions.insert (std::make_pair (&_start, s));
+	cmd.positions.insert (std::make_pair (&_end, e));
 }
 
 void
-Location::change_time_domain (Temporal::TimeDomain from, Temporal::TimeDomain to)
+Location::finish_domain_bounce (Temporal::DomainBounceInfo& cmd)
 {
-	if (_start.time_domain() == from) {
-		set_position_time_domain (to);
+	if (_start.time_domain() == cmd.to) {
+		/* had the right domain to begin with */
+		return;
 	}
+
+	TimeDomainPosChanges::iterator tpc;
+	timepos_t s;
+	timepos_t e;
+
+	tpc = cmd.positions.find (&_start);
+	assert (tpc != cmd.positions.end());
+	s = tpc->second;
+	s.set_time_domain (cmd.from);
+
+	tpc = cmd.positions.find (&_end);
+	assert (tpc != cmd.positions.end());
+	e = tpc->second;
+	e.set_time_domain (cmd.from);
+
+	set (s, e);
 }
 
 /*---------------------------------------------------------------------- */
 
 Locations::Locations (Session& s)
 	: SessionHandleRef (s)
+	, Temporal::TimeDomainProvider (s, false) /* session is our parent */
 {
 	current_location = 0;
 }
@@ -1890,21 +1917,28 @@ Locations::clear_cue_markers (samplepos_t start, samplepos_t end)
 }
 
 void
-Locations::globally_change_time_domain (Temporal::TimeDomain from, Temporal::TimeDomain to)
+Locations::start_domain_bounce (Temporal::DomainBounceInfo& cmd)
 {
 	Glib::Threads::RWLock::WriterLock lm (_lock);
-	for (auto & l : locations) {
-		l->globally_change_time_domain (from, to);
-	}
 
+	for (auto & l : locations) {
+		l->start_domain_bounce (cmd);
+	}
 }
 
 void
-Locations::change_time_domain (Temporal::TimeDomain from, Temporal::TimeDomain to)
+Locations::finish_domain_bounce (Temporal::DomainBounceInfo& cmd)
+{
+	for (auto & l : locations) {
+		l->finish_domain_bounce (cmd);
+	}
+}
+
+void
+Locations::time_domain_changed ()
 {
 	Glib::Threads::RWLock::WriterLock lm (_lock);
 	for (auto & l : locations) {
-		l->change_time_domain (from, to);
+		l->set_time_domain (time_domain());
 	}
-
 }
diff --git a/libs/ardour/midi_model.cc b/libs/ardour/midi_model.cc
index 7e993e7d97..5424f140af 100644
--- a/libs/ardour/midi_model.cc
+++ b/libs/ardour/midi_model.cc
@@ -1793,18 +1793,17 @@ MidiModel::create_mapping_stash (Temporal::Beats const & src_pos_offset)
 		Event<Beats>& off (n->off_event());
 		audio_time = tmap->superclock_at (src_pos_offset + off.time());
 		tempo_mapping_stash.insert (std::make_pair (&off, audio_time));
-
 	}
 
 	for (auto const & s : sysexes()) {
 		superclock_t audio_time = tmap->superclock_at (src_pos_offset + s->time());
-		tempo_mapping_stash.insert (std::make_pair ((void*)s.get(), audio_time));
+		tempo_mapping_stash.insert (std::make_pair (s.get(), audio_time));
 	}
 
 	for (uint8_t chan = 0; chan < 16; ++chan) {
 		for (auto const & p : pitches(chan)) {
 			superclock_t audio_time = tmap->superclock_at (src_pos_offset + p->time());
-			tempo_mapping_stash.insert (std::make_pair ((void*) &p, audio_time));
+			tempo_mapping_stash.insert (std::make_pair (p.get(), audio_time));
 		}
 	}
 
@@ -1827,6 +1826,7 @@ MidiModel::rebuild_from_mapping_stash (Temporal::Beats const & src_pos_offset)
 	}
 
 	TempoMap::SharedPtr tmap (TempoMap::use());
+	NoteDiffCommand* note_cmd = new_note_diff_command (_("conform to tempo map"));
 
 	for (auto & n : notes()) {
 
@@ -1836,17 +1836,21 @@ MidiModel::rebuild_from_mapping_stash (Temporal::Beats const & src_pos_offset)
 		TempoMappingStash::iterator tms (tempo_mapping_stash.find (&on));
 		assert (tms != tempo_mapping_stash.end());
 		Beats beat_time (tmap->quarters_at_superclock (tms->second) - src_pos_offset);
-		on.set_time (beat_time);
+
+		note_cmd->change (n, NoteDiffCommand::StartTime, beat_time);
 
 		tms = tempo_mapping_stash.find (&off);
 		assert (tms != tempo_mapping_stash.end());
 		beat_time = tmap->quarters_at_superclock (tms->second) - src_pos_offset;
 		off.set_time (beat_time);
 
+		note_cmd->change (n, NoteDiffCommand::Length, beat_time);
 	}
 
+	apply_diff_command_as_subcommand (_midi_source.session(), note_cmd);
+
 	for (auto & s : sysexes()) {
-		TempoMappingStash::iterator tms (tempo_mapping_stash.find ((void*) &s));
+		TempoMappingStash::iterator tms (tempo_mapping_stash.find (s.get()));
 		assert (tms != tempo_mapping_stash.end());
 		Beats beat_time (tmap->quarters_at_superclock (tms->second) - src_pos_offset);
 		s->set_time (beat_time);
@@ -1854,7 +1858,7 @@ MidiModel::rebuild_from_mapping_stash (Temporal::Beats const & src_pos_offset)
 
 	for (uint8_t chan = 0; chan < 16; ++chan) {
 		for (auto & p : pitches(chan)) {
-			TempoMappingStash::iterator tms (tempo_mapping_stash.find ((void*) &p));
+			TempoMappingStash::iterator tms (tempo_mapping_stash.find (p.get()));
 			assert (tms != tempo_mapping_stash.end());
 			Beats beat_time (tmap->quarters_at_superclock (tms->second) - src_pos_offset);
 			p->set_time (beat_time);
diff --git a/libs/ardour/midi_region.cc b/libs/ardour/midi_region.cc
index 8c1d4de5ca..57882752ea 100644
--- a/libs/ardour/midi_region.cc
+++ b/libs/ardour/midi_region.cc
@@ -614,23 +614,24 @@ MidiRegion::merge (std::shared_ptr<MidiRegion const> other_region)
 }
 
 void
-MidiRegion::swap_domain (Temporal::TimeDomain from, Temporal::TimeDomain to)
+MidiRegion::start_domain_bounce (Temporal::DomainBounceInfo& cmd)
 {
-	if (from == Temporal::BeatTime) {
-		model()->create_mapping_stash (source_position().beats());
-	} else {
-		model()->rebuild_from_mapping_stash (source_position().beats());
+	/* Deal with the region position & length */
 
-		_model_changed_connection.disconnect ();
-		model()->ContentsChanged ();
-		model()->ContentsChanged.connect_same_thread (_model_changed_connection, boost::bind (&MidiRegion::model_contents_changed, this));
+	Region::start_domain_bounce (cmd);
+	if (cmd.from == Temporal::BeatTime) {
+		model()->create_mapping_stash (source_position().beats());
 	}
 }
 
 void
-MidiRegion::globally_change_time_domain (Temporal::TimeDomain from, Temporal::TimeDomain to)
+MidiRegion::finish_domain_bounce (Temporal::DomainBounceInfo& cmd)
 {
-	Region::globally_change_time_domain (from, to);
-	swap_domain (from, to);
-	Temporal::domain_swap->add (*this);
+	Region::finish_domain_bounce (cmd);
+
+	model()->rebuild_from_mapping_stash (source_position().beats());
+
+	_model_changed_connection.disconnect ();
+	model()->ContentsChanged ();
+	model()->ContentsChanged.connect_same_thread (_model_changed_connection, boost::bind (&MidiRegion::model_contents_changed, this));
 }
diff --git a/libs/ardour/pannable.cc b/libs/ardour/pannable.cc
index badacaa4aa..e35a33dd74 100644
--- a/libs/ardour/pannable.cc
+++ b/libs/ardour/pannable.cc
@@ -266,3 +266,14 @@ Pannable::set_state (const XMLNode& root, int version)
 
 	return 0;
 }
+
+void
+Pannable::start_domain_bounce (Temporal::DomainBounceInfo&)
+{
+}
+
+void
+Pannable::finish_domain_bounce (Temporal::DomainBounceInfo&)
+{
+}
+
diff --git a/libs/ardour/playlist.cc b/libs/ardour/playlist.cc
index 81a8b6efa3..42a3bd89c3 100644
--- a/libs/ardour/playlist.cc
+++ b/libs/ardour/playlist.cc
@@ -3530,17 +3530,38 @@ Playlist::rdiff_and_add_command (Session* session)
 }
 
 void
-Playlist::globally_change_time_domain (Temporal::TimeDomain from, Temporal::TimeDomain to)
+Playlist::start_domain_bounce (Temporal::DomainBounceInfo& cmd)
 {
 	RegionReadLock rlock (this);
 	for (auto & region  : regions) {
-		region->globally_change_time_domain (from, to);
+		region->start_domain_bounce (cmd);
 	}
 }
 
+
+void
+Playlist::finish_domain_bounce (Temporal::DomainBounceInfo& cmd)
+{
+	ThawList thawlist;
+
+	clear_changes ();
+
+	{
+		RegionWriteLock rlock (this);
+		for (auto & region  : regions) {
+			thawlist.add (region);
+			region->finish_domain_bounce (cmd);
+		}
+	}
+
+	thawlist.release ();
+	rdiff_and_add_command (&_session);
+}
+
 void
 Playlist::time_domain_changed ()
 {
+#if 0
 	using namespace Temporal;
 
 	TimeDomainProvider::time_domain_changed ();
@@ -3549,8 +3570,8 @@ Playlist::time_domain_changed ()
 	Temporal::TimeDomain from = (to == AudioTime ? BeatTime : AudioTime);
 
 	for (auto & region  : regions) {
-		region->change_time_domain (from, to);
+		region->swap_time_domain (from, to);
 	}
-
+#endif
 }
 
diff --git a/libs/ardour/region.cc b/libs/ardour/region.cc
index 3dd0b01685..1372a670cf 100644
--- a/libs/ardour/region.cc
+++ b/libs/ardour/region.cc
@@ -2270,27 +2270,39 @@ Region::time_domain() const
 }
 
 void
-Region::globally_change_time_domain (Temporal::TimeDomain from, Temporal::TimeDomain to)
+Region::start_domain_bounce (Temporal::DomainBounceInfo& cmd)
 {
-	assert (Temporal::domain_swap);
+	if (locked()) {
+		return;
+	}
 
 	/* recall that the _length member is a timecnt_t, and so holds both
 	 * position *and* length.
 	 */
 
-	if (_length.val().time_domain() == from) {
-		timecnt_t& l (_length.non_const_val());
-		l.set_time_domain (to);
-		Temporal::domain_swap->add (l);
+	if (_length.val().time_domain() != cmd.from) {
+		return;
 	}
+
+	timecnt_t& l (_length.non_const_val());
+
+	timecnt_t  saved (l);
+	saved.set_time_domain (cmd.to);
+
+	cmd.counts.insert (std::make_pair (&l, saved));
 }
 
 void
-Region::change_time_domain (Temporal::TimeDomain from, Temporal::TimeDomain to)
+Region::finish_domain_bounce (Temporal::DomainBounceInfo& cmd)
 {
-	std::cerr << name() << " change td to " << to << std::endl;
-	if (_length.val().time_domain() == from) {
-		timecnt_t& l (_length.non_const_val());
-		l.set_time_domain (to);
-	}
+	clear_changes ();
+
+	Temporal::TimeDomainCntChanges::iterator tc = cmd.counts.find (&_length.non_const_val());
+	assert (tc != cmd.counts.end());
+
+	/* switch domains back (but with modified TempoMap, presumably */
+	tc->second.set_time_domain (cmd.from);
+	_length = tc->second;
+
+	send_change (Properties::length);
 }
diff --git a/libs/ardour/route.cc b/libs/ardour/route.cc
index 2c3f83c88c..912f03aa1d 100644
--- a/libs/ardour/route.cc
+++ b/libs/ardour/route.cc
@@ -6349,8 +6349,3 @@ Route::tempo_map_changed ()
 		_triggerbox->tempo_map_changed ();
 	}
 }
-
-void
-Route::globally_change_time_domain (Temporal::TimeDomain from, Temporal::TimeDomain to)
-{
-}
diff --git a/libs/ardour/session.cc b/libs/ardour/session.cc
index 776dbd912e..09718dee42 100644
--- a/libs/ardour/session.cc
+++ b/libs/ardour/session.cc
@@ -7787,15 +7787,3 @@ Session::foreach_route (void (Route::*method)())
 	}
 }
 
-void
-Session::time_domain_changed ()
-{
-	using namespace Temporal;
-
-	TimeDomainProvider::time_domain_changed ();
-
-	Temporal::TimeDomain to = time_domain();
-	Temporal::TimeDomain from = (to == AudioTime ? BeatTime : AudioTime);
-
-	_locations->change_time_domain (from, to);
-}
diff --git a/libs/ardour/session_playlists.cc b/libs/ardour/session_playlists.cc
index a1cd2427f8..afd1b0196c 100644
--- a/libs/ardour/session_playlists.cc
+++ b/libs/ardour/session_playlists.cc
@@ -689,11 +689,31 @@ SessionPlaylists::foreach (boost::function<void(std::shared_ptr<const Playlist>)
 }
 
 void
-SessionPlaylists::globally_change_time_domain (Temporal::TimeDomain from, Temporal::TimeDomain to)
+SessionPlaylists::start_domain_bounce (Temporal::DomainBounceInfo& cmd)
 {
 	Glib::Threads::Mutex::Lock lm (lock);
 
 	for (auto & pl : playlists) {
-		pl->globally_change_time_domain (from, to);
+		pl->start_domain_bounce (cmd);
+	}
+}
+
+void
+SessionPlaylists::finish_domain_bounce (Temporal::DomainBounceInfo& cmd)
+{
+	/* We cannot hold the playlist lock while finishing a domain bounce
+	 */
+
+	std::vector<std::shared_ptr<Playlist> > copy;
+
+	{
+		Glib::Threads::Mutex::Lock lm (lock);
+		for (auto & pl : playlists) {
+			copy.push_back (pl);
+		}
+	}
+
+	for (auto & pl : copy) {
+		pl->finish_domain_bounce (cmd);
 	}
 }
diff --git a/libs/ardour/session_state.cc b/libs/ardour/session_state.cc
index 6035d08845..cfacc6a2a2 100644
--- a/libs/ardour/session_state.cc
+++ b/libs/ardour/session_state.cc
@@ -3346,6 +3346,7 @@ Session::add_stateful_diff_command (std::shared_ptr<PBD::StatefulDestructible> s
 void
 Session::begin_reversible_command (const string& name)
 {
+	std::cerr << "begin REV-C [" << name << "]\n";
 	begin_reversible_command (g_quark_from_string (name.c_str ()));
 }
 
@@ -3395,6 +3396,7 @@ Session::abort_reversible_command ()
 	if (_current_trans != 0) {
 		DEBUG_UNDO_HISTORY (
 		    string_compose ("Abort Reversible Command: %1", _current_trans->name ()));
+		std::cerr << "abort REV-C [" << _current_trans->name() << "]\n";
 		_current_trans->clear();
 		delete _current_trans;
 		_current_trans = 0;
@@ -3421,6 +3423,7 @@ Session::commit_reversible_command (Command *cmd)
 		return;
 	}
 
+	std::cerr << "commit REV-C [" << _current_trans->name() << "]\n";
 	struct timeval now;
 
 	if (cmd) {
@@ -3460,6 +3463,8 @@ Session::commit_reversible_command (Command *cmd)
 	gettimeofday (&now, 0);
 	_current_trans->set_timestamp (now);
 
+	std::cerr << "Add command with " << _current_trans->size() << std::endl;
+
 	_history.add (_current_trans);
 	_current_trans = 0;
 }
diff --git a/libs/ardour/session_time.cc b/libs/ardour/session_time.cc
index d81890a979..62125f0e9d 100644
--- a/libs/ardour/session_time.cc
+++ b/libs/ardour/session_time.cc
@@ -299,21 +299,42 @@ Session::any_duration_to_samples (samplepos_t position, AnyTime const & duration
 	return duration.samples;
 }
 
-PBD::Command*
-Session::globally_change_time_domain (Temporal::TimeDomain from, Temporal::TimeDomain to)
+void
+Session::start_domain_bounce (Temporal::DomainBounceInfo& cmd)
 {
-	PBD::Command* undo_command = new Temporal::TimeDomainCommand (from, to);
-
 	{
 		std::shared_ptr<RouteList const> rl (routes.reader());
 
 		for (auto const& r : *rl) {
-			r->globally_change_time_domain (from, to);
+			r->start_domain_bounce (cmd);
 		}
 	}
 
-	_playlists->globally_change_time_domain (from, to);
-	_locations->globally_change_time_domain (from, to);
-
-	return undo_command;
+	_playlists->start_domain_bounce(cmd);
+	_locations->start_domain_bounce (cmd);
 }
+
+void
+Session::finish_domain_bounce (Temporal::DomainBounceInfo& cmd)
+{
+	{
+		std::shared_ptr<RouteList const> rl (routes.reader());
+
+		for (auto const& r : *rl) {
+			r->finish_domain_bounce (cmd);
+		}
+	}
+
+	_playlists->finish_domain_bounce (cmd);
+	_locations->finish_domain_bounce (cmd);
+}
+
+void
+Session::time_domain_changed ()
+{
+	TimeDomainProvider::time_domain_changed ();
+
+	// _playlists->set_time_domain (time_domain());
+	// _locations->set_time_domain (time_domain());
+}
+
diff --git a/libs/pbd/pbd/undo.h b/libs/pbd/pbd/undo.h
index 890d0a8a95..4736b31040 100644
--- a/libs/pbd/pbd/undo.h
+++ b/libs/pbd/pbd/undo.h
@@ -60,6 +60,8 @@ public:
 	void add_command (PBD::Command* const);
 	void remove_command (PBD::Command* const);
 
+	std::list<PBD::Command*>::size_type size() const { return actions.size(); }
+
 	void operator() ();
 	void undo ();
 	void redo ();
diff --git a/libs/temporal/domainswap.cc b/libs/temporal/domain_swap.cc
similarity index 56%
rename from libs/temporal/domainswap.cc
rename to libs/temporal/domain_swap.cc
index 5558062480..49d8eea6ba 100644
--- a/libs/temporal/domainswap.cc
+++ b/libs/temporal/domain_swap.cc
@@ -16,39 +16,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#include "temporal/domainswap.h"
+#include "temporal/domain_swap.h"
 
 using namespace Temporal;
 
-void
-TimeDomainCommand::add (TimeDomainSwapper& tds)
-{
-	tds.DropReferences.connect_same_thread (tds_connections, boost::bind (&TimeDomainCommand::going_away, this, &tds));
-	swappers.insert (&tds);
-}
-
-void
-TimeDomainCommand::going_away (TimeDomainSwapper* tds)
-{
-	Swappers::iterator i = swappers.find (tds);
-
-	if (i != swappers.end()) {
-		swappers.erase (i);
-	}
-}
-
-void
-TimeDomainCommand::operator() ()
-{
-	for (auto & swapper : swappers) {
-		swapper->swap_domain (from, to);
-	}
-}
-
-void
-TimeDomainCommand::undo ()
-{
-	for (auto & swapper : swappers) {
-		swapper->swap_domain (to, from);
-	}
-}
diff --git a/libs/temporal/tempo.cc b/libs/temporal/tempo.cc
index d08500a55b..d89552d665 100644
--- a/libs/temporal/tempo.cc
+++ b/libs/temporal/tempo.cc
@@ -4864,49 +4864,6 @@ TempoCommand::operator() ()
 	TempoMap::update (map);
 }
 
-DomainSwapInformation* Temporal::domain_swap (0);
-
-DomainSwapInformation*
-DomainSwapInformation::start(TimeDomain prev)
-{
-	TEMPO_MAP_ASSERT (!domain_swap);
-	domain_swap = new DomainSwapInformation (prev);
-	return domain_swap;
-}
-
-DomainSwapInformation::~DomainSwapInformation ()
-{
-	TEMPO_MAP_ASSERT (this == domain_swap);
-	undo ();
-	domain_swap = 0;
-}
-
-void
-DomainSwapInformation::clear ()
-{
-	counts.clear ();
-	positions.clear ();
-}
-
-void
-DomainSwapInformation::undo ()
-{
-	std::cerr << "DSI::undo on " << counts.size() << " lengths and " << positions.size() << " positions\n";
-	for (auto & c : counts) {
-		c->set_time_domain (previous);
-	}
-
-	for (auto & p : positions) {
-		p->set_time_domain (previous);
-	}
-
-	for (auto & tt : time_things) {
-		tt->swap_domain (previous == AudioTime ? BeatTime : AudioTime, previous);
-	}
-
-	clear ();
-}
-
 TempoMapCutBuffer::TempoMapCutBuffer (timecnt_t const & dur)
 	: _start_tempo (nullptr)
 	, _end_tempo (nullptr)
diff --git a/libs/temporal/temporal/domainswap.h b/libs/temporal/temporal/domain_swap.h
similarity index 52%
rename from libs/temporal/temporal/domainswap.h
rename to libs/temporal/temporal/domain_swap.h
index 5fd6d9c034..1630a19174 100644
--- a/libs/temporal/temporal/domainswap.h
+++ b/libs/temporal/temporal/domain_swap.h
@@ -30,56 +30,38 @@
 
 namespace Temporal {
 
+typedef std::map<timepos_t*,timepos_t> TimeDomainPosChanges;
+typedef std::map<timecnt_t*,timecnt_t> TimeDomainCntChanges;
+
+struct LIBTEMPORAL_API DomainBounceInfo;
+
 struct LIBTEMPORAL_API TimeDomainSwapper : public virtual PBD::Destructible {
-	virtual ~TimeDomainSwapper() {}
-	virtual void swap_domain (Temporal::TimeDomain from, Temporal::TimeDomain to) = 0;
-};
-
-
-struct LIBTEMPORAL_API TimeDomainCommand : public PBD::Command {
   public:
-	TimeDomainCommand (TimeDomain f, TimeDomain t) : from (f), to (t) {}
-	void add (TimeDomainSwapper&);
-
-	void operator() ();
-	void undo ();
-
-  private:
-	TimeDomain from;
-	TimeDomain to;
-
-	typedef std::set<TimeDomainSwapper*> Swappers;
-	Swappers swappers;
-	PBD::ScopedConnectionList tds_connections;
-
-	void going_away (TimeDomainSwapper*);
-
+	virtual ~TimeDomainSwapper() {}
+	virtual void start_domain_bounce (DomainBounceInfo&) = 0;
+	virtual void finish_domain_bounce (DomainBounceInfo&) = 0;
 };
 
-class LIBTEMPORAL_API DomainSwapInformation {
-   public:
-	static DomainSwapInformation* start (TimeDomain prev);
+/* A DomainBounceInfo functions in two roles:
+ *
+ * 1. as part of an UndoTransaction reflecting actions taken by a user that
+ * modified time domains of one or more objects.
+ *
+ * 2. as a standalone object used during temporary domain swaps that records
+ * (perhaps opaquely) what was changed and provides a way to revert it.
+ */
 
-	~DomainSwapInformation ();
+struct LIBTEMPORAL_API DomainBounceInfo
+{
+	DomainBounceInfo (TimeDomain f, TimeDomain t) : from (f), to (t) {}
 
-	void add (timecnt_t& t) { counts.push_back (&t); }
-	void add (timepos_t& p) { positions.push_back (&p); }
-	void add (TimeDomainSwapper& tt) { time_things.push_back (&tt); }
-	void clear ();
+	const TimeDomain from;
+	const TimeDomain to;
 
-   private:
-	DomainSwapInformation (TimeDomain prev) : previous (prev) {}
-
-	std::vector<timecnt_t*> counts;
-	std::vector<timepos_t*> positions;
-	std::vector<TimeDomainSwapper*> time_things;
-	TimeDomain previous;
-
-	void undo ();
+	TimeDomainPosChanges positions;
+	TimeDomainCntChanges counts;
 };
 
-extern LIBTEMPORAL_API DomainSwapInformation* domain_swap;
-
 }
 
 #endif /* __tmeporal_domain_swap_h__ */
diff --git a/libs/temporal/temporal/tempo.h b/libs/temporal/temporal/tempo.h
index e24e70a4e2..0b2df9c1dd 100644
--- a/libs/temporal/temporal/tempo.h
+++ b/libs/temporal/temporal/tempo.h
@@ -42,7 +42,7 @@
 #include "temporal/beats.h"
 #include "temporal/bbt_argument.h"
 #include "temporal/bbt_time.h"
-#include "temporal/domainswap.h"
+#include "temporal/domain_swap.h"
 #include "temporal/superclock.h"
 #include "temporal/timeline.h"
 #include "temporal/types.h"
diff --git a/libs/temporal/wscript b/libs/temporal/wscript
index bbdbc620c1..9fe008f52f 100644
--- a/libs/temporal/wscript
+++ b/libs/temporal/wscript
@@ -28,7 +28,7 @@ temporal_sources = [
     'debug.cc',
     'bbt_time.cc',
     'beats.cc',
-    'domainswap.cc',
+    'domain_swap.cc',
     'enums.cc',
     'range.cc',
     'superclock.cc',