diff --git a/gtk2_ardour/midi_region_view.cc b/gtk2_ardour/midi_region_view.cc
index e3179e0f94..230136c72d 100644
--- a/gtk2_ardour/midi_region_view.cc
+++ b/gtk2_ardour/midi_region_view.cc
@@ -33,6 +33,7 @@
 #include "pbd/stateful_diff_command.h"
 
 #include "ardour/midi_model.h"
+#include "ardour/midi_playlist.h"
 #include "ardour/midi_region.h"
 #include "ardour/midi_source.h"
 #include "ardour/midi_track.h"
@@ -1066,6 +1067,9 @@ MidiRegionView::apply_diff (bool as_subcommand)
 		}
 	}
 
+	midi_view()->midi_track()->midi_playlist()->region_edited(
+		_region, _note_diff_command);
+
 	if (as_subcommand) {
 		_model->apply_command_as_subcommand (*trackview.session(), _note_diff_command);
 	} else {
@@ -1074,7 +1078,6 @@ MidiRegionView::apply_diff (bool as_subcommand)
 	}
 
 	_note_diff_command = 0;
-	midi_view()->midi_track()->playlist_modified();
 
 	if (add_or_remove) {
 		_marked_for_selection.clear();
diff --git a/libs/ardour/ardour/midi_model.h b/libs/ardour/ardour/midi_model.h
index 4214431280..b2e018ca3b 100644
--- a/libs/ardour/ardour/midi_model.h
+++ b/libs/ardour/ardour/midi_model.h
@@ -126,7 +126,6 @@ public:
 
 		static Variant::Type value_type (Property prop);
 
-	private:
 		struct NoteChange {
 			NoteDiffCommand::Property property;
 			NotePtr note;
@@ -135,12 +134,17 @@ public:
 			Variant new_value;
 		};
 
-		typedef std::list<NoteChange> ChangeList;
-		ChangeList _changes;
-
+		typedef std::list<NoteChange>                                    ChangeList;
 		typedef std::list< boost::shared_ptr< Evoral::Note<TimeType> > > NoteList;
-		NoteList _added_notes;
-		NoteList _removed_notes;
+
+		const ChangeList& changes()       const { return _changes; }
+		const NoteList&   added_notes()   const { return _added_notes; }
+		const NoteList&   removed_notes() const { return _removed_notes; }
+
+	private:
+		ChangeList _changes;
+		NoteList   _added_notes;
+		NoteList   _removed_notes;
 
 		std::set<NotePtr> side_effect_removals;
 
@@ -285,6 +289,8 @@ public:
 	void insert_silence_at_start (TimeType);
 	void transpose (TimeType, TimeType, int);
 
+	std::set<WeakNotePtr>& active_notes() { return _active_notes; }
+
 protected:
 	int resolve_overlaps_unlocked (const NotePtr, void* arg = 0);
 
@@ -302,7 +308,6 @@ private:
 
 public:
 	WriteLock edit_lock();
-	WriteLock write_lock();
 
 private:
 	friend class DeltaCommand;
@@ -319,6 +324,8 @@ private:
 	// We cannot use a boost::shared_ptr here to avoid a retain cycle
 	boost::weak_ptr<MidiSource> _midi_source;
 	InsertMergePolicy _insert_merge_policy;
+
+	std::set<WeakNotePtr> _active_notes;
 };
 
 } /* namespace ARDOUR */
diff --git a/libs/ardour/ardour/midi_playlist.h b/libs/ardour/ardour/midi_playlist.h
index f49593bd85..614a5e1c1f 100644
--- a/libs/ardour/ardour/midi_playlist.h
+++ b/libs/ardour/ardour/midi_playlist.h
@@ -23,8 +23,15 @@
 #include <vector>
 #include <list>
 
+#include <boost/utility.hpp>
+
 #include "ardour/ardour.h"
+#include "ardour/midi_model.h"
+#include "ardour/midi_state_tracker.h"
+#include "ardour/note_fixer.h"
 #include "ardour/playlist.h"
+#include "evoral/Beats.hpp"
+#include "evoral/Note.hpp"
 #include "evoral/Parameter.hpp"
 
 namespace Evoral {
@@ -34,10 +41,10 @@ template<typename Time> class EventSink;
 namespace ARDOUR
 {
 
-class Session;
+class BeatsFramesConverter;
 class MidiRegion;
+class Session;
 class Source;
-class MidiStateTracker;
 
 template<typename T> class MidiRingBuffer;
 
@@ -80,6 +87,15 @@ public:
 
 	std::set<Evoral::Parameter> contained_automation();
 
+	/** Handle a region edit during read.
+	 *
+	 * This must be called before the command is applied to the model.  Events
+	 * are injected into the playlist output to compensate for edits to active
+	 * notes and maintain coherent output and tracker state.
+	 */
+	void region_edited(boost::shared_ptr<Region>         region,
+	                   const MidiModel::NoteDiffCommand* cmd);
+
 	/** Clear all note trackers. */
 	void reset_note_trackers ();
 
@@ -91,18 +107,24 @@ public:
 	void resolve_note_trackers (Evoral::EventSink<framepos_t>& dst, framepos_t time);
 
 protected:
-
 	void remove_dependents (boost::shared_ptr<Region> region);
 
 private:
+	typedef Evoral::Note<Evoral::Beats> Note;
+	typedef Evoral::Event<framepos_t>   Event;
+
+	struct RegionTracker : public boost::noncopyable {
+		MidiStateTracker tracker;  ///< Active note tracker
+		NoteFixer        fixer;    ///< Edit compensation
+	};
+
+	typedef std::map< Region*, boost::shared_ptr<RegionTracker> > NoteTrackers;
+
 	void dump () const;
 
-	bool region_changed (const PBD::PropertyChange&, boost::shared_ptr<Region>);
-
-	NoteMode _note_mode;
-
-	typedef std::map<Region*,MidiStateTracker*> NoteTrackers;
 	NoteTrackers _note_trackers;
+	NoteMode     _note_mode;
+	framepos_t   _read_end;
 };
 
 } /* namespace ARDOUR */
diff --git a/libs/ardour/ardour/midi_region.h b/libs/ardour/ardour/midi_region.h
index ece23b65f0..f7e6c97ea0 100644
--- a/libs/ardour/ardour/midi_region.h
+++ b/libs/ardour/ardour/midi_region.h
@@ -32,11 +32,6 @@ class XMLNode;
 
 namespace ARDOUR {
 	namespace Properties {
-		/* this is pseudo-property: nothing has this as an actual
-		   property, but it allows us to signal changes to the
-		   MidiModel used by the MidiRegion
-		*/
-		LIBARDOUR_API extern PBD::PropertyDescriptor<void*> midi_data;
 		LIBARDOUR_API extern PBD::PropertyDescriptor<Evoral::Beats> start_beats;
 		LIBARDOUR_API extern PBD::PropertyDescriptor<Evoral::Beats> length_beats;
 	}
@@ -141,7 +136,6 @@ class LIBARDOUR_API MidiRegion : public Region
 
 	void model_changed ();
 	void model_automation_state_changed (Evoral::Parameter const &);
-	void model_contents_changed ();
 
 	void set_start_beats_from_start_frames ();
 	void update_after_tempo_map_change ();
diff --git a/libs/ardour/ardour/midi_source.h b/libs/ardour/ardour/midi_source.h
index 8a0c13681d..156f3dbfa0 100644
--- a/libs/ardour/ardour/midi_source.h
+++ b/libs/ardour/ardour/midi_source.h
@@ -154,8 +154,12 @@ class LIBARDOUR_API MidiSource : virtual public Source, public boost::enable_sha
 	virtual void load_model(const Glib::Threads::Mutex::Lock& lock, bool force_reload=false) = 0;
 	virtual void destroy_model(const Glib::Threads::Mutex::Lock& lock) = 0;
 
-	/** Reset cached information (like iterators) when things have changed. */
-	void invalidate(const Glib::Threads::Mutex::Lock& lock);
+	/** Reset cached information (like iterators) when things have changed.
+	 * @param lock Source lock, which must be held by caller.
+	 * @param notes If non-NULL, currently active notes are added to this set.
+	 */
+	void invalidate(const Glib::Threads::Mutex::Lock&                       lock,
+	                std::set<Evoral::Sequence<Evoral::Beats>::WeakNotePtr>* notes=NULL);
 
 	void set_note_mode(const Glib::Threads::Mutex::Lock& lock, NoteMode mode);
 
diff --git a/libs/ardour/ardour/note_fixer.h b/libs/ardour/ardour/note_fixer.h
new file mode 100644
index 0000000000..09f45cdec7
--- /dev/null
+++ b/libs/ardour/ardour/note_fixer.h
@@ -0,0 +1,102 @@
+/*
+    Copyright (C) 2015 Paul Davis
+    Author: David Robillard
+
+    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., 675 Mass Ave, Cambridge, MA 02139, USA.
+*/
+
+#ifndef __ardour_note_fixer_h__
+#define __ardour_note_fixer_h__
+
+#include <list>
+
+#include <boost/utility.hpp>
+
+#include "ardour/midi_model.h"
+#include "ardour/types.h"
+#include "evoral/Beats.hpp"
+#include "evoral/Note.hpp"
+
+namespace Evoral { template<typename Time> class EventSink; }
+
+namespace ARDOUR {
+
+class BeatsFramesConverter;
+class MidiStateTracker;
+class TempoMap;
+
+/** A tracker and compensator for note edit operations.
+ *
+ * This monitors edit operations sent to a model that affect active notes
+ * during a read, and maintains a queue of synthetic events that should be sent
+ * at the start of the next read to maintain coherent MIDI state.
+ */
+class NoteFixer : public boost::noncopyable
+{
+public:
+	typedef Evoral::Note<Evoral::Beats> Note;
+
+	~NoteFixer();
+
+	/** Clear all internal state. */
+	void clear();
+
+	/** Handle a region edit during read.
+	 *
+	 * This must be called before the command is applied to the model.  Events
+	 * are enqueued to compensate for edits which should be later sent with
+	 * emit() at the start of the next read.
+	 *
+	 * @param cmd Command to compensate for.
+	 * @param origin Timeline position of edited source.
+	 * @param pos Current read position (last read end).
+	 */
+	void prepare(TempoMap&                          tempo_map,
+	             const MidiModel::NoteDiffCommand*  cmd,
+	             framepos_t                         origin,
+	             framepos_t                         pos,
+	             std::set< boost::weak_ptr<Note> >& active_notes);
+
+	/** Emit any pending edit compensation events.
+	 *
+	 * @param dst Destination for events.
+	 * @param pos Timestamp to be used for every event, should be the start of
+	 * the read block immediately following any calls to prepare().
+	 * @param tracker Tracker to update with emitted events.
+	 */
+	void emit(Evoral::EventSink<framepos_t>& dst,
+	          framepos_t                     pos,
+	          MidiStateTracker&              tracker);
+
+private:
+	typedef Evoral::Event<framepos_t> Event;
+	typedef std::list<Event*>         Events;
+
+	/** Copy a beats event to a frames event with the given time stamp. */
+	Event* copy_event(framepos_t time, const Evoral::Event<Evoral::Beats>& ev);
+
+	/** Return true iff `note` is active at `pos`. */
+	bool note_is_active(const BeatsFramesConverter& converter,
+	                    boost::shared_ptr<Note>     note,
+	                    framepos_t                  pos);
+
+	Events _events;
+};
+
+} /* namespace ARDOUR */
+
+#endif	/* __ardour_note_fixer_h__ */
+
+
diff --git a/libs/ardour/midi_model.cc b/libs/ardour/midi_model.cc
index 7e88569adc..de5000669c 100644
--- a/libs/ardour/midi_model.cc
+++ b/libs/ardour/midi_model.cc
@@ -1612,27 +1612,21 @@ MidiModel::find_sysex (gint sysex_id)
 MidiModel::WriteLock
 MidiModel::edit_lock()
 {
-	boost::shared_ptr<MidiSource> ms = _midi_source.lock ();
-	assert (ms);
+	boost::shared_ptr<MidiSource> ms          = _midi_source.lock();
+	Glib::Threads::Mutex::Lock*   source_lock = 0;
+
+	if (ms) {
+		/* Take source lock and invalidate iterator to release its lock on model.
+		   Add currently active notes to _active_notes so we can restore them
+		   if playback resumes at the same point after the edit. */
+		source_lock = new Glib::Threads::Mutex::Lock(ms->mutex());
+		ms->invalidate(*source_lock,
+		               ms->session().transport_rolling() ? &_active_notes : NULL);
+	}
 
-	Glib::Threads::Mutex::Lock* source_lock = new Glib::Threads::Mutex::Lock (ms->mutex());
-	ms->invalidate(*source_lock); // Release cached iterator's read lock on model
 	return WriteLock(new WriteLockImpl(source_lock, _lock, _control_lock));
 }
 
-/** Lock just the model, the source lock must already be held.
- * This should only be called from libardour/evoral places
- */
-MidiModel::WriteLock
-MidiModel::write_lock()
-{
-	boost::shared_ptr<MidiSource> ms = _midi_source.lock ();
-	assert (ms);
-
-	assert (!ms->mutex().trylock ());
-	return WriteLock(new WriteLockImpl(0, _lock, _control_lock));
-}
-
 int
 MidiModel::resolve_overlaps_unlocked (const NotePtr note, void* arg)
 {
diff --git a/libs/ardour/midi_playlist.cc b/libs/ardour/midi_playlist.cc
index 60753d0baa..398234e2ba 100644
--- a/libs/ardour/midi_playlist.cc
+++ b/libs/ardour/midi_playlist.cc
@@ -17,21 +17,22 @@
     Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */
 
-#include <cassert>
-
 #include <algorithm>
+#include <cassert>
+#include <cstdlib>
 #include <iostream>
 #include <utility>
 
-#include <stdlib.h>
-
 #include "evoral/EventList.hpp"
 
+#include "ardour/beats_frames_converter.h"
 #include "ardour/debug.h"
 #include "ardour/midi_model.h"
 #include "ardour/midi_playlist.h"
 #include "ardour/midi_region.h"
+#include "ardour/midi_source.h"
 #include "ardour/midi_state_tracker.h"
+#include "ardour/session.h"
 #include "ardour/types.h"
 
 #include "i18n.h"
@@ -43,6 +44,7 @@ using namespace std;
 MidiPlaylist::MidiPlaylist (Session& session, const XMLNode& node, bool hidden)
 	: Playlist (session, node, DataType::MIDI, hidden)
 	, _note_mode(Sustained)
+	, _read_end(0)
 {
 #ifndef NDEBUG
 	const XMLProperty* prop = node.property("type");
@@ -61,12 +63,14 @@ MidiPlaylist::MidiPlaylist (Session& session, const XMLNode& node, bool hidden)
 MidiPlaylist::MidiPlaylist (Session& session, string name, bool hidden)
 	: Playlist (session, name, DataType::MIDI, hidden)
 	, _note_mode(Sustained)
+	, _read_end(0)
 {
 }
 
 MidiPlaylist::MidiPlaylist (boost::shared_ptr<const MidiPlaylist> other, string name, bool hidden)
 	: Playlist (other, name, hidden)
 	, _note_mode(other->_note_mode)
+	, _read_end(0)
 {
 }
 
@@ -77,6 +81,7 @@ MidiPlaylist::MidiPlaylist (boost::shared_ptr<const MidiPlaylist> other,
                             bool                                  hidden)
 	: Playlist (other, start, dur, name, hidden)
 	, _note_mode(other->_note_mode)
+	, _read_end(0)
 {
 }
 
@@ -103,13 +108,18 @@ struct EventsSortByTimeAndType {
 framecnt_t
 MidiPlaylist::read (Evoral::EventSink<framepos_t>& dst, framepos_t start, framecnt_t dur, unsigned chan_n)
 {
+	typedef pair<MidiStateTracker*,framepos_t> TrackerInfo;
+
 	Playlist::RegionReadLock rl (this);
 
 	DEBUG_TRACE (DEBUG::MidiPlaylistIO,
 	             string_compose ("---- MidiPlaylist::read %1 .. %2 (%3 trackers) ----\n",
 	                             start, start + dur, _note_trackers.size()));
 
-	typedef pair<MidiStateTracker*,framepos_t> TrackerInfo;
+	/* First, emit any queued edit fixup events at start. */
+	for (NoteTrackers::iterator t = _note_trackers.begin(); t != _note_trackers.end(); ++t) {
+		t->second->fixer.emit(dst, _read_end, t->second->tracker);
+	}
 
 	/* Find relevant regions that overlap [start..end] */
 	const framepos_t                         end = start + dur - 1;
@@ -158,11 +168,11 @@ MidiPlaylist::read (Evoral::EventSink<framepos_t>& dst, framepos_t start, framec
 		}
 
 		/* Get the existing note tracker for this region, or create a new one. */
-		NoteTrackers::iterator t           = _note_trackers.find (mr.get());
-		MidiStateTracker*      tracker     = NULL;
-		bool                   new_tracker = false;
+		NoteTrackers::iterator           t           = _note_trackers.find (mr.get());
+		bool                             new_tracker = false;
+		boost::shared_ptr<RegionTracker> tracker;
 		if (t == _note_trackers.end()) {
-			tracker = new MidiStateTracker;
+			tracker     = boost::shared_ptr<RegionTracker>(new RegionTracker);
 			new_tracker = true;
 			DEBUG_TRACE (DEBUG::MidiPlaylistIO,
 			             string_compose ("\tPre-read %1 (%2 .. %3): new tracker\n",
@@ -171,13 +181,13 @@ MidiPlaylist::read (Evoral::EventSink<framepos_t>& dst, framepos_t start, framec
 			tracker = t->second;
 			DEBUG_TRACE (DEBUG::MidiPlaylistIO,
 			             string_compose ("\tPre-read %1 (%2 .. %3): %4 active notes\n",
-			                             mr->name(), mr->position(), mr->last_frame(), tracker->on()));
+			                             mr->name(), mr->position(), mr->last_frame(), tracker->tracker.on()));
 		}
 
-		/** Read from region into target. */
-		mr->read_at (tgt, start, dur, chan_n, _note_mode, tracker);
+		/* Read from region into target. */
+		mr->read_at (tgt, start, dur, chan_n, _note_mode, &tracker->tracker);
 		DEBUG_TRACE (DEBUG::MidiPlaylistIO,
-		             string_compose ("\tPost-read: %1 active notes\n", tracker->on()));
+		             string_compose ("\tPost-read: %1 active notes\n", tracker->tracker.on()));
 
 		if (find (ended.begin(), ended.end(), *i) != ended.end()) {
 			/* Region ended within the read range, so resolve any active notes
@@ -187,8 +197,7 @@ MidiPlaylist::read (Evoral::EventSink<framepos_t>& dst, framepos_t start, framec
 			             string_compose ("\t%1 ended, resolve notes and delete (%2) tracker\n",
 			                             mr->name(), ((new_tracker) ? "new" : "old")));
 
-			tracker->resolve_notes (tgt, (*i)->last_frame());
-			delete tracker;
+			tracker->tracker.resolve_notes (tgt, (*i)->last_frame());
 			if (!new_tracker) {
 				_note_trackers.erase (t);
 			}
@@ -216,17 +225,40 @@ MidiPlaylist::read (Evoral::EventSink<framepos_t>& dst, framepos_t start, framec
 	}
 
 	DEBUG_TRACE (DEBUG::MidiPlaylistIO, "---- End MidiPlaylist::read ----\n");
+	_read_end = start + dur;
 	return dur;
 }
 
+void
+MidiPlaylist::region_edited(boost::shared_ptr<Region>         region,
+                            const MidiModel::NoteDiffCommand* cmd)
+{
+	typedef MidiModel::NoteDiffCommand Command;
+
+	boost::shared_ptr<MidiRegion> mr = boost::dynamic_pointer_cast<MidiRegion>(region);
+	if (!mr || !_session.transport_rolling()) {
+		return;
+	}
+
+	/* Take write lock to prevent concurrency with read(). */
+	Playlist::RegionWriteLock lock(this);
+
+	NoteTrackers::iterator t = _note_trackers.find(mr.get());
+	if (t == _note_trackers.end()) {
+		return; /* Region is not currently active, nothing to do. */
+	}
+
+	/* Queue any necessary edit compensation events. */
+	t->second->fixer.prepare(
+		_session.tempo_map(), cmd, mr->position() - mr->start(),
+		_read_end, mr->midi_source()->model()->active_notes());
+}
+
 void
 MidiPlaylist::reset_note_trackers ()
 {
 	Playlist::RegionWriteLock rl (this, false);
 
-	for (NoteTrackers::iterator n = _note_trackers.begin(); n != _note_trackers.end(); ++n) {
-		delete n->second;
-	}
 	DEBUG_TRACE (DEBUG::MidiTrackers, string_compose ("%1 reset all note trackers\n", name()));
 	_note_trackers.clear ();
 }
@@ -237,8 +269,7 @@ MidiPlaylist::resolve_note_trackers (Evoral::EventSink<framepos_t>& dst, framepo
 	Playlist::RegionWriteLock rl (this, false);
 
 	for (NoteTrackers::iterator n = _note_trackers.begin(); n != _note_trackers.end(); ++n) {
-		n->second->resolve_notes(dst, time);
-		delete n->second;
+		n->second->tracker.resolve_notes(dst, time);
 	}
 	DEBUG_TRACE (DEBUG::MidiTrackers, string_compose ("%1 resolve all note trackers\n", name()));
 	_note_trackers.clear ();
@@ -248,14 +279,7 @@ void
 MidiPlaylist::remove_dependents (boost::shared_ptr<Region> region)
 {
 	/* MIDI regions have no dependents (crossfades) but we might be tracking notes */
-	NoteTrackers::iterator t = _note_trackers.find (region.get());
-
-	/* GACK! THREAD SAFETY! */
-
-	if (t != _note_trackers.end()) {
-		delete t->second;
-		_note_trackers.erase (t);
-	}
+	_note_trackers.erase(region.get());
 }
 
 int
@@ -355,24 +379,3 @@ MidiPlaylist::contained_automation()
 
 	return ret;
 }
-
-
-bool
-MidiPlaylist::region_changed (const PBD::PropertyChange& what_changed, boost::shared_ptr<Region> region)
-{
-	if (in_flush || in_set_state) {
-		return false;
-	}
-
-	PBD::PropertyChange our_interests;
-	our_interests.add (Properties::midi_data);
-
-	bool parent_wants_notify = Playlist::region_changed (what_changed, region);
-
-	if (parent_wants_notify || what_changed.contains (our_interests)) {
-		notify_contents_changed ();
-	}
-
-	return true;
-}
-
diff --git a/libs/ardour/midi_region.cc b/libs/ardour/midi_region.cc
index c02caff470..5c197761ac 100644
--- a/libs/ardour/midi_region.cc
+++ b/libs/ardour/midi_region.cc
@@ -53,7 +53,6 @@ using namespace PBD;
 
 namespace ARDOUR {
 	namespace Properties {
-		PBD::PropertyDescriptor<void*>         midi_data;
 		PBD::PropertyDescriptor<Evoral::Beats> start_beats;
 		PBD::PropertyDescriptor<Evoral::Beats> length_beats;
 	}
@@ -62,8 +61,6 @@ namespace ARDOUR {
 void
 MidiRegion::make_property_quarks ()
 {
-	Properties::midi_data.property_id = g_quark_from_static_string (X_("midi-data"));
-	DEBUG_TRACE (DEBUG::Properties, string_compose ("quark for midi-data = %1\n", Properties::midi_data.property_id));
 	Properties::start_beats.property_id = g_quark_from_static_string (X_("start-beats"));
 	DEBUG_TRACE (DEBUG::Properties, string_compose ("quark for start-beats = %1\n", Properties::start_beats.property_id));
 	Properties::length_beats.property_id = g_quark_from_static_string (X_("length-beats"));
@@ -245,11 +242,16 @@ MidiRegion::master_read_at (MidiRingBuffer<framepos_t>& out, framepos_t position
 }
 
 framecnt_t
-MidiRegion::_read_at (const SourceList& /*srcs*/, Evoral::EventSink<framepos_t>& dst, framepos_t position, framecnt_t dur, uint32_t chan_n,
-		      NoteMode mode, MidiStateTracker* tracker) const
+MidiRegion::_read_at (const SourceList&              /*srcs*/,
+                      Evoral::EventSink<framepos_t>& dst,
+                      framepos_t                     position,
+                      framecnt_t                     dur,
+                      uint32_t                       chan_n,
+                      NoteMode                       mode,
+                      MidiStateTracker*              tracker) const
 {
 	frameoffset_t internal_offset = 0;
-	framecnt_t to_read         = 0;
+	framecnt_t    to_read         = 0;
 
 	/* precondition: caller has verified that we cover the desired section */
 
@@ -408,24 +410,6 @@ MidiRegion::model_changed ()
 	midi_source()->AutomationStateChanged.connect_same_thread (
 		_model_connection, boost::bind (&MidiRegion::model_automation_state_changed, this, _1)
 		);
-
-	model()->ContentsChanged.connect_same_thread (
-	        _model_contents_connection, boost::bind (&MidiRegion::model_contents_changed, this));
-}
-
-void
-MidiRegion::model_contents_changed ()
-{
-	{
-		/* Invalidate source iterator to force reading new contents even if the
-		   calls to read() progress linearly.  Try-lock only to avoid deadlock
-		   when called while writing with the source already locked. */
-		Glib::Threads::Mutex::Lock lm (midi_source(0)->mutex(), Glib::Threads::TRY_LOCK);
-		if (lm.locked()) {
-			midi_source(0)->invalidate (lm);
-		}
-	}
-	send_change (PropertyChange (Properties::midi_data));
 }
 
 void
@@ -448,6 +432,7 @@ MidiRegion::model_automation_state_changed (Evoral::Parameter const & p)
 	*/
 	Glib::Threads::Mutex::Lock lm (midi_source(0)->mutex(), Glib::Threads::TRY_LOCK);
 	if (lm.locked()) {
+		/* TODO: This is too aggressive, we need more fine-grained invalidation. */
 		midi_source(0)->invalidate (lm);
 	}
 }
diff --git a/libs/ardour/midi_source.cc b/libs/ardour/midi_source.cc
index 8d3b130594..47cfb1b0a0 100644
--- a/libs/ardour/midi_source.cc
+++ b/libs/ardour/midi_source.cc
@@ -177,10 +177,10 @@ MidiSource::update_length (framecnt_t)
 }
 
 void
-MidiSource::invalidate (const Lock& lock)
+MidiSource::invalidate (const Lock& lock, std::set<Evoral::Sequence<Evoral::Beats>::WeakNotePtr>* notes)
 {
 	_model_iter_valid = false;
-	_model_iter.invalidate();
+	_model_iter.invalidate(notes);
 }
 
 framecnt_t
@@ -201,10 +201,15 @@ MidiSource::midi_read (const Lock&                        lm,
 	if (_model) {
 		// Find appropriate model iterator
 		Evoral::Sequence<Evoral::Beats>::const_iterator& i = _model_iter;
-		if (_last_read_end == 0 || start != _last_read_end || !_model_iter_valid) {
+		const bool linear_read = _last_read_end != 0 && start == _last_read_end;
+		if (!linear_read || !_model_iter_valid) {
 			// Cached iterator is invalid, search for the first event past start
-			i                 = _model->begin(converter.from(start), false, filtered);
+			i = _model->begin(converter.from(start), false, filtered,
+			                  linear_read ? &_model->active_notes() : NULL);
 			_model_iter_valid = true;
+			if (!linear_read) {
+				_model->active_notes().clear();
+			}
 		}
 
 		_last_read_end = start + cnt;
diff --git a/libs/ardour/note_fixer.cc b/libs/ardour/note_fixer.cc
new file mode 100644
index 0000000000..749d873779
--- /dev/null
+++ b/libs/ardour/note_fixer.cc
@@ -0,0 +1,145 @@
+/*
+    Copyright (C) 2015 Paul Davis
+    Author: David Robillard
+
+    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., 675 Mass Ave, Cambridge, MA 02139, USA.
+*/
+
+#include "evoral/EventList.hpp"
+
+#include "ardour/beats_frames_converter.h"
+#include "ardour/midi_state_tracker.h"
+#include "ardour/note_fixer.h"
+#include "ardour/tempo.h"
+
+namespace ARDOUR {
+
+NoteFixer::~NoteFixer()
+{
+	clear();
+}
+
+void
+NoteFixer::clear()
+{
+	for (Events::iterator i = _events.begin(); i != _events.end(); ++i) {
+		delete *i;
+	}
+}
+
+void
+NoteFixer::prepare(TempoMap&                          tempo_map,
+                   const MidiModel::NoteDiffCommand*  cmd,
+                   const framepos_t                   origin,
+                   const framepos_t                   pos,
+                   std::set< boost::weak_ptr<Note> >& active_notes)
+{
+	typedef MidiModel::NoteDiffCommand Command;
+
+	BeatsFramesConverter converter(tempo_map, origin);
+
+	for (Command::NoteList::const_iterator i = cmd->removed_notes().begin();
+	     i != cmd->removed_notes().end(); ++i) {
+		if (note_is_active(converter, *i, pos)) {
+			/* Deleted note spans the end of the latest read, so we will never
+			   read its off event.  Emit a note off to prevent a stuck note. */
+			_events.push_back(copy_event(pos, (*i)->off_event()));
+			active_notes.erase(*i);
+		}
+	}
+
+	for (Command::NoteList::const_iterator i = cmd->added_notes().begin();
+	     i != cmd->added_notes().end(); ++i) {
+		if (note_is_active(converter, *i, pos)) {
+			/* Added note spans the end of the latest read, so we missed its on
+			   event.  Emit note on immediately to make the state consistent. */
+			_events.push_back(copy_event(pos, (*i)->on_event()));
+			active_notes.insert(*i);
+		}
+	}
+
+	for (Command::ChangeList::const_iterator i = cmd->changes().begin();
+	     i != cmd->changes().end(); ++i) {
+		if (!note_is_active(converter, i->note, pos)) {
+			/* Note is not currently active, no compensation needed. */
+			continue;
+		}
+
+		/* Changed note spans the end of the latest read. */
+		if (i->property == Command::NoteNumber) {
+			/* Note number has changed, end the old note. */
+			_events.push_back(copy_event(pos, i->note->off_event()));
+
+			/* Start a new note on the new note number.  The same note object
+			   is active, so we leave active_notes alone. */
+			Event* on = copy_event(pos, i->note->on_event());
+			on->buffer()[1] = (uint8_t)i->new_value.get_int();
+			_events.push_back(on);
+		} else if (i->property == Command::StartTime &&
+		           converter.to(i->new_value.get_beats()) >= pos) {
+			/* Start time has moved from before to after the end of the
+			   latest read, end the old note. */
+			_events.push_back(copy_event(pos, i->note->off_event()));
+			active_notes.erase(i->note);
+		} else if (i->property == Command::Length &&
+		           converter.to(i->note->time() + i->new_value.get_beats()) < pos) {
+			/* Length has shortened to before the end of the latest read,
+			   end the note. */
+			_events.push_back(copy_event(pos, i->note->off_event()));
+			active_notes.erase(i->note);
+		} else if (i->property == Command::Channel) {
+			/* Channel has changed, end the old note. */
+			_events.push_back(copy_event(pos, i->note->off_event()));
+
+			/* Start a new note on the new channel.  See number change above. */
+			Event* on = copy_event(pos, i->note->on_event());
+			on->buffer()[0] &= 0xF0;
+			on->buffer()[0] |= (uint8_t)i->new_value.get_int();
+			_events.push_back(on);
+		}
+	}
+}
+
+void
+NoteFixer::emit(Evoral::EventSink<framepos_t>& dst,
+                framepos_t                     pos,
+                MidiStateTracker&              tracker)
+{
+	for (Events::iterator i = _events.begin(); i != _events.end(); ++i) {
+		dst.write(pos, (*i)->event_type(), (*i)->size(), (*i)->buffer());
+		tracker.track(**i);
+		delete *i;
+	}
+	_events.clear();
+}
+
+NoteFixer::Event*
+NoteFixer::copy_event(framepos_t time, const Evoral::Event<Evoral::Beats>& ev)
+{
+	return new Event(ev.event_type(), time, ev.size(), ev.buffer());
+}
+
+bool
+NoteFixer::note_is_active(const BeatsFramesConverter& converter,
+                          boost::shared_ptr<Note>     note,
+                          framepos_t                  pos)
+{
+	const framepos_t start_time = converter.to(note->time());
+	const framepos_t end_time   = converter.to(note->end_time());
+
+	return (start_time < pos && end_time >= pos);
+}
+
+} // namespace ARDOUR
diff --git a/libs/ardour/wscript b/libs/ardour/wscript
index 9b2e9c4b2c..293915cd74 100644
--- a/libs/ardour/wscript
+++ b/libs/ardour/wscript
@@ -132,6 +132,7 @@ libardour_sources = [
         'mididm.cc',
         'mtdm.cc',
         'mute_master.cc',
+        'note_fixer.cc',
         'onset_detector.cc',
         'operations.cc',
         'pan_controllable.cc',
diff --git a/libs/evoral/evoral/Event.hpp b/libs/evoral/evoral/Event.hpp
index 1682028335..ec92d575d0 100644
--- a/libs/evoral/evoral/Event.hpp
+++ b/libs/evoral/evoral/Event.hpp
@@ -49,6 +49,8 @@ public:
 #ifdef EVORAL_EVENT_ALLOC
 	Event (EventType type=0, Time time=Time(), uint32_t size=0, uint8_t* buf=NULL, bool alloc=false);
 
+	Event (EventType type, Time time, uint32_t size, const uint8_t* buf);
+
 	/** Copy \a copy.
 	 *
 	 * If \a alloc is true, the buffer will be copied and this method
diff --git a/libs/evoral/evoral/Sequence.hpp b/libs/evoral/evoral/Sequence.hpp
index 639a85730c..a5e95de1be 100644
--- a/libs/evoral/evoral/Sequence.hpp
+++ b/libs/evoral/evoral/Sequence.hpp
@@ -82,14 +82,15 @@ protected:
 
 public:
 
-	typedef typename boost::shared_ptr<Evoral::Note<Time> >  NotePtr;
-	typedef typename boost::shared_ptr<const Evoral::Note<Time> >  constNotePtr;
+	typedef typename boost::shared_ptr<Evoral::Note<Time> >       NotePtr;
+	typedef typename boost::weak_ptr<Evoral::Note<Time> >         WeakNotePtr;
+	typedef typename boost::shared_ptr<const Evoral::Note<Time> > constNotePtr;
 
 	typedef boost::shared_ptr<Glib::Threads::RWLock::ReaderLock> ReadLock;
-	typedef boost::shared_ptr<WriteLockImpl>            WriteLock;
+	typedef boost::shared_ptr<WriteLockImpl>                     WriteLock;
 
 	virtual ReadLock  read_lock() const { return ReadLock(new Glib::Threads::RWLock::ReaderLock(_lock)); }
-        virtual WriteLock write_lock()      { return WriteLock(new WriteLockImpl(_lock, _control_lock)); }
+	virtual WriteLock write_lock()      { return WriteLock(new WriteLockImpl(_lock, _control_lock)); }
 
 	void clear();
 
@@ -182,7 +183,7 @@ public:
 	OverlapPitchResolution overlap_pitch_resolution() const { return _overlap_pitch_resolution; }
 	void set_overlap_pitch_resolution(OverlapPitchResolution opr);
 
-	void set_notes (const typename Sequence<Time>::Notes& n);
+	void set_notes (const Sequence<Time>::Notes& n);
 
 	typedef boost::shared_ptr< Event<Time> > SysExPtr;
 	typedef boost::shared_ptr<const Event<Time> > constSysExPtr;
@@ -220,13 +221,15 @@ public:
 	class LIBEVORAL_API const_iterator {
 	public:
 		const_iterator();
-		const_iterator(const Sequence<Time>& seq, Time t, bool, std::set<Evoral::Parameter> const &);
-		~const_iterator();
+		const_iterator(const Sequence<Time>&              seq,
+		               Time                               t,
+		               bool                               force_discrete,
+		               const std::set<Evoral::Parameter>& filtered,
+		               const std::set<WeakNotePtr>*       active_notes=NULL);
 
 		inline bool valid() const { return !_is_end && _event; }
-		//inline bool locked() const { return _locked; }
 
-		void invalidate();
+		void invalidate(std::set<WeakNotePtr>* notes);
 
 		const Event<Time>& operator*()  const { return *_event;  }
 		const boost::shared_ptr< Event<Time> > operator->() const  { return _event; }
@@ -267,10 +270,11 @@ public:
 	};
 
 	const_iterator begin (
-		Time t = Time(),
-		bool force_discrete = false,
-		std::set<Evoral::Parameter> const & f = std::set<Evoral::Parameter> ()) const {
-		return const_iterator (*this, t, force_discrete, f);
+		Time                               t              = Time(),
+		bool                               force_discrete = false,
+		const std::set<Evoral::Parameter>& f              = std::set<Evoral::Parameter>(),
+		const std::set<WeakNotePtr>*       active_notes   = NULL) const {
+		return const_iterator (*this, t, force_discrete, f, active_notes);
 	}
 
 	const const_iterator& end() const { return _end_iter; }
diff --git a/libs/evoral/src/Event.cpp b/libs/evoral/src/Event.cpp
index 66e45ab2ad..da31662951 100644
--- a/libs/evoral/src/Event.cpp
+++ b/libs/evoral/src/Event.cpp
@@ -63,6 +63,22 @@ Event<Timestamp>::Event(EventType type, Timestamp time, uint32_t size, uint8_t*
 	}
 }
 
+template<typename Timestamp>
+Event<Timestamp>::Event(EventType      type,
+                        Timestamp      time,
+                        uint32_t       size,
+                        const uint8_t* buf)
+	: _type(type)
+	, _original_time(time)
+	, _nominal_time(time)
+	, _size(size)
+	, _buf((uint8_t*)malloc(size))
+	, _id(-1)
+	, _owns_buf(true)
+{
+	memcpy(_buf, buf, _size);
+}
+
 template<typename Timestamp>
 Event<Timestamp>::Event(const Event& copy, bool owns_buf)
 	: _type(copy._type)
diff --git a/libs/evoral/src/Sequence.cpp b/libs/evoral/src/Sequence.cpp
index 1d52a12e4f..c8a0dd4f23 100644
--- a/libs/evoral/src/Sequence.cpp
+++ b/libs/evoral/src/Sequence.cpp
@@ -72,7 +72,11 @@ Sequence<Time>::const_iterator::const_iterator()
 
 /** @param force_discrete true to force ControlLists to use discrete evaluation, otherwise false to get them to use their configured mode */
 template<typename Time>
-Sequence<Time>::const_iterator::const_iterator(const Sequence<Time>& seq, Time t, bool force_discrete, std::set<Evoral::Parameter> const & filtered)
+Sequence<Time>::const_iterator::const_iterator(const Sequence<Time>&              seq,
+                                               Time                               t,
+                                               bool                               force_discrete,
+                                               const std::set<Evoral::Parameter>& filtered,
+                                               const std::set<WeakNotePtr>*       active_notes)
 	: _seq(&seq)
 	, _active_patch_change_message (0)
 	, _type(NIL)
@@ -91,6 +95,17 @@ Sequence<Time>::const_iterator::const_iterator(const Sequence<Time>& seq, Time t
 
 	_lock = seq.read_lock();
 
+	// Add currently active notes, if given
+	if (active_notes) {
+		for (typename std::set<WeakNotePtr>::const_iterator i = active_notes->begin();
+		     i != active_notes->end(); ++i) {
+			NotePtr note = i->lock();
+			if (note && note->time() <= t && note->end_time() > t) {
+				_active_notes.push(note);
+			}
+		}
+	}
+
 	// Find first note which begins at or after t
 	_note_iter = seq.note_lower_bound(t);
 
@@ -192,16 +207,14 @@ Sequence<Time>::const_iterator::const_iterator(const Sequence<Time>& seq, Time t
 	}
 }
 
-template<typename Time>
-Sequence<Time>::const_iterator::~const_iterator()
-{
-}
-
 template<typename Time>
 void
-Sequence<Time>::const_iterator::invalidate()
+Sequence<Time>::const_iterator::invalidate(std::set< boost::weak_ptr< Note<Time> > >* notes)
 {
 	while (!_active_notes.empty()) {
+		if (notes) {
+			notes->insert(_active_notes.top());
+		}
 		_active_notes.pop();
 	}
 	_type = NIL;
@@ -278,7 +291,7 @@ Sequence<Time>::const_iterator::set_event()
 		DEBUG_TRACE(DEBUG::Sequence, "iterator = note off\n");
 		assert(!_active_notes.empty());
 		*_event = _active_notes.top()->off_event();
-		_active_notes.pop();
+		// We don't pop the active note until we increment past it
 		break;
 	case SYSEX:
 		DEBUG_TRACE(DEBUG::Sequence, "iterator = sysex\n");
@@ -338,6 +351,7 @@ Sequence<Time>::const_iterator::operator++()
 		++_note_iter;
 		break;
 	case NOTE_OFF:
+		_active_notes.pop();
 		break;
 	case CONTROL:
 		// Increment current controller iterator