diff --git a/libs/ardour/ardour/midi_source.h b/libs/ardour/ardour/midi_source.h
index e5f800e27b..50d5496a9c 100644
--- a/libs/ardour/ardour/midi_source.h
+++ b/libs/ardour/ardour/midi_source.h
@@ -148,12 +148,10 @@ class LIBARDOUR_API MidiSource : virtual public Source
 	 *
 	 * @param position The timeline position the source now starts at.
 	 * @param capture_length The current length of the capture, which may not
-	 * be zero if record is armed while rolling.
-	 * @param loop_length The loop length if looping, otherwise zero.
+	 * be zero if record is armed while rolling. In samples because we
+	 * record using timestamps derived from the audio engine.
 	 */
-	void mark_write_starting_now (samplecnt_t position,
-	                              samplecnt_t capture_length,
-	                              samplecnt_t loop_length);
+	void mark_write_starting_now (timepos_t const & position, samplecnt_t capture_length);
 
 	/* like ::mark_streaming_write_completed() but with more arguments to
 	 * allow control over MIDI-specific behaviour. Expected to be used only
@@ -233,10 +231,7 @@ class LIBARDOUR_API MidiSource : virtual public Source
 	bool                         _writing;
 
 	/** The total duration of the current capture. */
-	samplepos_t _capture_length;
-
-	/** Length of transport loop during current capture, or zero. */
-	samplepos_t _capture_loop_length;
+	samplecnt_t _capture_length;
 
 	/** Map of interpolation styles to use for Parameters; if they are not in this map,
 	 *  the correct interpolation style can be obtained from EventTypeMap::interpolation_of ()
diff --git a/libs/ardour/disk_writer.cc b/libs/ardour/disk_writer.cc
index 6b30e8d4a9..3200f6d24b 100644
--- a/libs/ardour/disk_writer.cc
+++ b/libs/ardour/disk_writer.cc
@@ -395,8 +395,16 @@ void
 DiskWriter::non_realtime_locate (samplepos_t position)
 {
 	if (_midi_write_source) {
-#warning NUTEMPO maybe fixme perhaps take sources time domain into account here e.g. beats
-		_midi_write_source->set_natural_position (timepos_t (position));
+		timepos_t pos;
+
+		if (time_domain() == Temporal::AudioTime) {
+			pos = timepos_t (position);
+		} else {
+			const timepos_t b (position);
+			pos = timepos_t (b.beats());
+		}
+
+		_midi_write_source->set_natural_position (pos);
 	}
 
 	DiskIOProcessor::non_realtime_locate (position);
@@ -524,7 +532,14 @@ DiskWriter::run (BufferSet& bufs, samplepos_t start_sample, samplepos_t end_samp
 
 			if (_midi_write_source) {
 				assert (_capture_start_sample);
-				_midi_write_source->mark_write_starting_now (_capture_start_sample, _capture_captured, loop_length.samples());
+
+				timepos_t start (_capture_start_sample);
+
+				if (time_domain() != Temporal::AudioTime) {
+					start = timepos_t (start.beats());
+				}
+
+				_midi_write_source->mark_write_starting_now (start, _capture_captured);
 			}
 
 			g_atomic_int_set (&_samples_pending_write, 0);
diff --git a/libs/ardour/midi_source.cc b/libs/ardour/midi_source.cc
index f47f87cd0b..7e76a32dd9 100644
--- a/libs/ardour/midi_source.cc
+++ b/libs/ardour/midi_source.cc
@@ -67,7 +67,6 @@ MidiSource::MidiSource (Session& s, string name, Source::Flag flags)
 	: Source(s, DataType::MIDI, name, flags)
 	, _writing(false)
 	, _capture_length(0)
-	, _capture_loop_length(0)
 {
 }
 
@@ -75,7 +74,6 @@ MidiSource::MidiSource (Session& s, const XMLNode& node)
 	: Source(s, node)
 	, _writing(false)
 	, _capture_length(0)
-	, _capture_loop_length(0)
 {
 	if (set_state (node, Stateful::loading_state_version)) {
 		throw failed_constructor();
@@ -324,9 +322,7 @@ MidiSource::mark_streaming_midi_write_started (const Lock& lock, NoteMode mode)
 }
 
 void
-MidiSource::mark_write_starting_now (samplecnt_t position,
-                                     samplecnt_t capture_length,
-                                     samplecnt_t loop_length)
+MidiSource::mark_write_starting_now (timepos_t const & position, samplecnt_t capture_length)
 {
 	/* I'm not sure if this is the best way to approach this, but
 	   _capture_length needs to be set up with the transport sample
@@ -339,10 +335,9 @@ MidiSource::mark_write_starting_now (samplecnt_t position,
 	   because it is not RT-safe.
 	*/
 
-#warning NUTEMPO QUESTION should the time domain here reflect some setting for this source?
-	set_natural_position (timepos_t (position));
+	set_natural_position (position);
+
 	_capture_length      = capture_length;
-	_capture_loop_length = loop_length;
 
 	/* currently prefer to compute length in beats, since that matches 6.x
 	 * and earlier behavior