diff --git a/libs/ardour/internal_send.cc b/libs/ardour/internal_send.cc
index a86051ccb3..8e5dd817c2 100644
--- a/libs/ardour/internal_send.cc
+++ b/libs/ardour/internal_send.cc
@@ -107,7 +107,7 @@ InternalSend::propagate_solo ()
 		/* propagate further downstream alike Route::input_change_handler() */
 		std::shared_ptr<RouteList const> routes = _session.get_routes ();
 		for (auto const& i : *routes) {
-			if (i == _send_to || i->is_master() || i->is_monitor() || i->is_auditioner()) {
+			if (i == _send_to || i->is_singleton () || i->is_auditioner()) {
 				continue;
 			}
 			bool does_feed = _send_to->feeds (i);
@@ -247,6 +247,7 @@ InternalSend::run (BufferSet& bufs, samplepos_t start_sample, samplepos_t end_sa
 				}
 			}
 		}
+
 	} else if (role () == Listen) {
 		/* We're going to the monitor bus, so discard MIDI data */
 
diff --git a/libs/ardour/route.cc b/libs/ardour/route.cc
index ee7e29382d..3cea82fdff 100644
--- a/libs/ardour/route.cc
+++ b/libs/ardour/route.cc
@@ -155,7 +155,7 @@ int
 Route::init ()
 {
 	/* default master bus to use strict i/o */
-	if (is_master() || is_monitor ()) {
+	if (is_singleton ()) {
 		_strict_io = true;
 		_meter_point = _pending_meter_point = MeterOutput;
 	}
@@ -221,7 +221,7 @@ Route::init ()
 		_amp->set_display_name (_("Monitor"));
 	}
 
-	if (!is_master() && !is_monitor() && !is_auditioner()) {
+	if (!is_singleton () && !is_auditioner ()) {
 		_delayline.reset (new DelayLine (_session, name ()));
 	}
 
@@ -5435,7 +5435,7 @@ Route::setup_invisible_processors ()
 		}
 	}
 
-	if (!is_master() && !is_monitor() && !is_auditioner()) {
+	if (!is_singleton () && !is_auditioner()) {
 		ProcessorList::iterator reader_pos = find (new_processors.begin(), new_processors.end(), _disk_reader);
 		if (reader_pos != new_processors.end()) {
 			/* insert before disk-reader */
diff --git a/libs/ardour/selection.cc b/libs/ardour/selection.cc
index 2dac79745d..11a7477a9b 100644
--- a/libs/ardour/selection.cc
+++ b/libs/ardour/selection.cc
@@ -163,7 +163,7 @@ CoreSelection::select_stripable_and_maybe_group (std::shared_ptr<Stripable> s, b
 
 	/* monitor is never selectable */
 
-	if (s->is_monitor()) {
+	if (s->is_monitor() || s->is_surround_master ()) {
 		return false;
 	}
 
diff --git a/libs/ardour/session.cc b/libs/ardour/session.cc
index ddc7eab165..fc5a9d1bb9 100644
--- a/libs/ardour/session.cc
+++ b/libs/ardour/session.cc
@@ -2724,7 +2724,7 @@ Session::ensure_stripable_sort_order ()
 	for (StripableList::iterator si = sl.begin(); si != sl.end(); ++si) {
 		std::shared_ptr<Stripable> s (*si);
 		assert (!s->is_auditioner ()); // XXX remove me
-		if (s->is_monitor ()) {
+		if (s->is_monitor () || s->is_surround_master ()) {
 			continue;
 		}
 		if (order != s->presentation_info().order()) {
@@ -3519,7 +3519,7 @@ Session::add_internal_send (std::shared_ptr<Route> dest, int index, std::shared_
 void
 Session::add_internal_send (std::shared_ptr<Route> dest, std::shared_ptr<Processor> before, std::shared_ptr<Route> sender)
 {
-	if (sender->is_monitor() || sender->is_master() || sender == dest || dest->is_monitor() || dest->is_master()) {
+	if (sender->is_singleton() || sender == dest || dest->is_singleton()) {
 		return;
 	}
 
@@ -4363,7 +4363,7 @@ Session::reassign_track_numbers ()
 		assert (!(*i)->is_auditioner());
 		if (std::dynamic_pointer_cast<Track> (*i)) {
 			(*i)->set_track_number(++tn);
-		} else if (!(*i)->is_master() && !(*i)->is_monitor()) {
+		} else if (!(*i)->is_main_bus ()) {
 			(*i)->set_track_number(--bn);
 		}
 
diff --git a/libs/ardour/session_state.cc b/libs/ardour/session_state.cc
index 2692e9d3eb..10ca7e1fa1 100644
--- a/libs/ardour/session_state.cc
+++ b/libs/ardour/session_state.cc
@@ -1118,7 +1118,7 @@ Session::export_track_state (std::shared_ptr<RouteList> rl, const string& path)
 		if ((*i)->is_auditioner()) {
 			continue;
 		}
-		if ((*i)->is_master() || (*i)->is_monitor()) {
+		if ((*i)->is_singleton()) {
 			continue;
 		}
 		child->add_child_nocopy ((*i)->get_state());
diff --git a/libs/ardour/stripable.cc b/libs/ardour/stripable.cc
index 5e4f185346..085514f37d 100644
--- a/libs/ardour/stripable.cc
+++ b/libs/ardour/stripable.cc
@@ -141,10 +141,12 @@ Stripable::Sorter::operator() (std::shared_ptr<ARDOUR::Stripable> a, std::shared
 	int cmp_a = 0;
 	int cmp_b = 0;
 
-	if (a->is_auditioner ()) { cmp_a = -2; }
-	if (b->is_auditioner ()) { cmp_b = -2; }
-	if (a->is_monitor ())    { cmp_a = -1; }
-	if (b->is_monitor ())    { cmp_b = -1; }
+	if (a->is_auditioner ())      { cmp_a = -3; }
+	if (b->is_auditioner ())      { cmp_b = -3; }
+	if (a->is_monitor ())         { cmp_a = -2; }
+	if (b->is_monitor ())         { cmp_b = -2; }
+	if (a->is_surround_master ()) { cmp_a = -1; }
+	if (b->is_surround_master ()) { cmp_b = -1; }
 
 	/* ARDOUR-Editor: [Track|Bus|Master] (0) < VCA (3)
 	 * ARDOUR-Mixer : [Track|Bus] (0) < VCA (3) < Master (4)
diff --git a/libs/ardour/vst3_plugin.cc b/libs/ardour/vst3_plugin.cc
index bb2c5e8ef1..62ee687d51 100644
--- a/libs/ardour/vst3_plugin.cc
+++ b/libs/ardour/vst3_plugin.cc
@@ -2649,7 +2649,7 @@ VST3PI::stripable_property_changed (PBD::PropertyChange const&)
 
 	std::string ns;
 	int order_key;
-	if (s->is_master ()) {
+	if (s->is_master () || s->is_surround_master ()) {
 		ns = _("Master");
 		order_key = 2;
 	} else if (s->is_monitor ()) {
@@ -2815,7 +2815,7 @@ VST3PI::getContextInfoValue (int32& value, FIDString id)
 	if (0 == strcmp (id, ContextInfo::kIndexMode)) {
 		value = ContextInfo::kFlatIndex;
 	} else if (0 == strcmp (id, ContextInfo::kType)) {
-		if (s->is_master ()) {
+		if (s->is_singleton ()) {
 			value = ContextInfo::kOut;
 		} else if (s->presentation_info ().flags () & PresentationInfo::AudioTrack) {
 			value = ContextInfo::kTrack;
@@ -2825,7 +2825,7 @@ VST3PI::getContextInfoValue (int32& value, FIDString id)
 			value = ContextInfo::kBus;
 		}
 	} else if (0 == strcmp (id, ContextInfo::kMain)) {
-		value = s->is_master () ? 1 : 0;
+		value = s->is_singleton () ? 1 : 0;
 	} else if (0 == strcmp (id, ContextInfo::kIndex)) {
 		value = s->presentation_info ().order ();
 	} else if (0 == strcmp (id, ContextInfo::kColor)) {
diff --git a/libs/surfaces/faderport8/actions.cc b/libs/surfaces/faderport8/actions.cc
index d448dd1d8f..f26cc16eac 100644
--- a/libs/surfaces/faderport8/actions.cc
+++ b/libs/surfaces/faderport8/actions.cc
@@ -276,7 +276,7 @@ FaderPort8::button_automation (ARDOUR::AutoState as)
 	StripableList all;
 	session->get_stripables (all);
 	for (StripableList::const_iterator i = all.begin(); i != all.end(); ++i) {
-		if ((*i)->is_master() || (*i)->is_monitor()) {
+		if ((*i)->is_singleton ()) {
 			continue;
 		}
 		if (!(*i)->is_selected()) {
@@ -328,7 +328,7 @@ FaderPort8::button_solo_clear ()
 		StripableList all;
 		session->get_stripables (all);
 		for (StripableList::const_iterator i = all.begin(); i != all.end(); ++i) {
-			if ((*i)->is_master() || (*i)->is_auditioner() || (*i)->is_monitor()) {
+			if ((*i)->is_singleton () || (*i)->is_auditioner()) {
 				continue;
 			}
 			std::shared_ptr<SoloControl> sc = (*i)->solo_control();
diff --git a/libs/surfaces/faderport8/faderport8.cc b/libs/surfaces/faderport8/faderport8.cc
index 533f92f37c..029a1589fc 100644
--- a/libs/surfaces/faderport8/faderport8.cc
+++ b/libs/surfaces/faderport8/faderport8.cc
@@ -968,6 +968,7 @@ FaderPort8::filter_stripables (StripableList& strips) const
 
 	bool allow_master = false;
 	bool allow_monitor = false;
+	bool allow_surround = false;
 
 	switch (_ctrls.mix_mode ()) {
 		case MixAudio:
@@ -987,11 +988,13 @@ FaderPort8::filter_stripables (StripableList& strips) const
 			break;
 		case MixUser:
 			allow_master = true;
+			allow_surround = true;
 			flt = &flt_selected;
 			break;
 		case MixOutputs:
 			allow_master = true;
 			allow_monitor = true;
+			allow_surround = true;
 			flt = &flt_mains;
 			break;
 		case MixInputs:
@@ -1005,6 +1008,7 @@ FaderPort8::filter_stripables (StripableList& strips) const
 			/* fallthrough */
 		case MixAll:
 			allow_master = true;
+			allow_surround = true;
 			flt = &flt_all;
 			break;
 	}
@@ -1018,6 +1022,7 @@ FaderPort8::filter_stripables (StripableList& strips) const
 
 		if (!allow_master  && (*s)->is_master ()) { continue; }
 		if (!allow_monitor && (*s)->is_monitor ()) { continue; }
+		if (!allow_surround && (*s)->is_surround_master ()) { continue; }
 
 		if ((*flt)(*s)) {
 			strips.push_back (*s);
diff --git a/libs/surfaces/mackie/mcp_buttons.cc b/libs/surfaces/mackie/mcp_buttons.cc
index 69ea5cfc31..5732ee2fbc 100644
--- a/libs/surfaces/mackie/mcp_buttons.cc
+++ b/libs/surfaces/mackie/mcp_buttons.cc
@@ -1260,8 +1260,7 @@ MackieControlProtocol::prog2_clear_solo_press (Button &)
 		for (StripableList::const_iterator i = sl.begin(); i != sl.end(); ++i)
 		{
 			std::shared_ptr<MuteControl> mc = (*i)->mute_control();
-			if (!mc->muted() && (!(*i)->is_master()) && (!(*i)->is_monitor()))
-			{
+			if (!mc->muted() && !(*i)->is_singleton ()) {
 				mc->set_value(1.0, Controllable::UseGroup);
 			}
 		}
diff --git a/libs/surfaces/osc/osc.cc b/libs/surfaces/osc/osc.cc
index 345437810c..506b68f2bb 100644
--- a/libs/surfaces/osc/osc.cc
+++ b/libs/surfaces/osc/osc.cc
@@ -1065,6 +1065,8 @@ OSC::routes_list (lo_message msg)
 				lo_message_add_string (reply, "MA");
 			} else if (s->is_monitor()) {
 				lo_message_add_string (reply, "MO");
+			} else if (s->is_surround_master()) {
+				lo_message_add_string (reply, "SM");
 			} else if (std::dynamic_pointer_cast<Route>(s) && !std::dynamic_pointer_cast<Track>(s)) {
 				if (!(s->presentation_info().flags() & PresentationInfo::MidiBus)) {
 					if (s->is_foldbackbus()) {
diff --git a/session_utils/copy-mixer.cc b/session_utils/copy-mixer.cc
index deaf40eff4..95697f0b8a 100644
--- a/session_utils/copy-mixer.cc
+++ b/session_utils/copy-mixer.cc
@@ -138,7 +138,7 @@ copy_session_routes (
 	/* get route state from first session */
 	std::shared_ptr<RouteList const> rl = s->get_routes ();
 	for (auto const& r : *rl) {
-		if (r->is_master () || r->is_monitor () || r->is_auditioner ()) {
+		if (r->is_singleton () || r->is_auditioner ()) {
 			continue;
 		}
 		XMLNode& state (r->get_state ());
@@ -178,7 +178,7 @@ copy_session_routes (
 	rl = s->get_routes ();
 	for (auto const& r : *rl) {
 		/* skip special busses */
-		if (r->is_master () || r->is_monitor () || r->is_auditioner ()) {
+		if (r->is_singleton () || r->is_auditioner ()) {
 			continue;
 		}
 		if (std::dynamic_pointer_cast<Track> (r)) {
@@ -204,7 +204,7 @@ copy_session_routes (
 	rl = s->get_routes ();
 	for (auto const& r : *rl) {
 		/* skip special busses */
-		if (r->is_master () || r->is_monitor () || r->is_auditioner ()) {
+		if (r->is_singleton () || r->is_auditioner ()) {
 			continue;
 		}
 		if (!std::dynamic_pointer_cast<Track> (r)) {