diff --git a/libs/ardour/delayline.cc b/libs/ardour/delayline.cc
index 8e5d8c4227..d3f4982f79 100644
--- a/libs/ardour/delayline.cc
+++ b/libs/ardour/delayline.cc
@@ -231,30 +231,34 @@ DelayLine::run (BufferSet& bufs, samplepos_t /* start_sample */, samplepos_t /*
 				dly->silence (n_samples);
 			}
 
-			// If the delay time changes, iterate over all events in the dly-buffer
-			// and adjust the time in-place. <= 0 becomes 0.
-			//
-			// iterate over all events in dly-buffer and subtract one cycle
-			// (n_samples) from the timestamp, bringing them closer to de-queue.
-			for (MidiBuffer::iterator m = dly->begin (); m != dly->end (); ++m) {
-				MidiBuffer::TimeType *t = m.timeptr ();
-				if (*t > n_samples + delay_diff) {
-					*t -= n_samples + delay_diff;
-				} else {
-					*t = 0;
+			if (delay_diff != 0) {
+				/* If the delay time changes, iterate over all events in the dly-buffer
+				 * and adjust the time in-place. <= 0 becomes 0.
+				 *
+				 * iterate over all events in dly-buffer and subtract one cycle
+				 * (n_samples) from the timestamp, bringing them closer to de-queue.
+				 */
+				for (MidiBuffer::iterator m = dly->begin (); m != dly->end (); ++m) {
+					MidiBuffer::TimeType *t = m.timeptr ();
+					if (*t > n_samples + delay_diff) {
+						*t -= n_samples + delay_diff;
+					} else {
+						*t = 0;
+					}
 				}
 			}
 
 			if (_delay != 0) {
-				// delay events in current-buffer, in place.
+				/* delay events in current-buffer, in place. */
 				for (MidiBuffer::iterator m = mb.begin (); m != mb.end (); ++m) {
 					MidiBuffer::TimeType *t = m.timeptr ();
 					*t += _delay;
 				}
 			}
 
-			// move events from dly-buffer into current-buffer until n_samples
-			// and remove them from the dly-buffer
+			/* move events from dly-buffer into current-buffer until n_samples
+			 * and remove them from the dly-buffer
+			 */
 			for (MidiBuffer::iterator m = dly->begin (); m != dly->end ();) {
 				const Evoral::Event<MidiBuffer::TimeType> ev (*m, false);
 				if (ev.time () >= n_samples) {
@@ -269,14 +273,19 @@ DelayLine::run (BufferSet& bufs, samplepos_t /* start_sample */, samplepos_t /*
 			 * (ie '_global_port_buffer_offset + _port_buffer_offset' - midi_port.cc)
 			 */
 			if (_delay != 0) {
-				// move events after n_samples from current-buffer into dly-buffer
-				// and trim current-buffer after n_samples
+				/* move events after n_samples from current-buffer into dly-buffer
+				 * and trim current-buffer after n_samples
+				 */
 				for (MidiBuffer::iterator m = mb.begin (); m != mb.end ();) {
 					const Evoral::Event<MidiBuffer::TimeType> ev (*m, false);
 					if (ev.time () < n_samples) {
 						++m;
 						continue;
 					}
+					/* insert_event() is expensive, if delay_diff is zero, the
+					 * event must be later than the last event in the delay-buffer
+					 * and push_back() would be preferable.
+					 */
 					dly->insert_event (ev);
 					m = mb.erase (m);
 				}
diff --git a/libs/ardour/fixed_delay.cc b/libs/ardour/fixed_delay.cc
index b55e4f6f56..6606197047 100644
--- a/libs/ardour/fixed_delay.cc
+++ b/libs/ardour/fixed_delay.cc
@@ -131,6 +131,39 @@ FixedDelay::delay (
 	assert (id < _buffers[dt].size ());
 	DelayBuffer *db = _buffers[dt][id];
 
+	ARDOUR::MidiBuffer const* mb;
+	if ((mb = dynamic_cast<ARDOUR::MidiBuffer const*> (&in))) {
+		ARDOUR::MidiBuffer* mout =  dynamic_cast<ARDOUR::MidiBuffer*> (&out);
+		ARDOUR::MidiBuffer* mdly =  dynamic_cast<ARDOUR::MidiBuffer*> (db->buf);
+		assert (mout && mdly);
+
+		mout->clear ();
+
+		/* delay events from input buffer and append them to the
+		 * corresponding buffer.
+		 */
+		for (MidiBuffer::const_iterator m = mb->begin (); m != mb->end (); ++m) {
+			Evoral::Event<MidiBuffer::TimeType> ev (*m, false);
+			ev.set_time (ev.time () + _delay);
+			if (ev.time () < n_samples) {
+				mout->push_back (ev);
+			} else {
+				mdly->push_back (ev);
+			}
+		}
+
+		/* move events from the delay-buffer into output */
+		for (MidiBuffer::iterator m = mdly->begin (); m != mdly->end ();) {
+			const Evoral::Event<MidiBuffer::TimeType> ev (*m, false);
+			if (ev.time () >= n_samples) {
+				break;
+			}
+			mout->push_back (ev);
+			m = mdly->erase (m);
+		}
+		return;
+	}
+
 	if (db->pos + n_samples > _buf_size) {
 		uint32_t w0 = _buf_size - db->pos;
 		uint32_t w1 = db->pos + n_samples - _buf_size;