diff --git a/gtk2_ardour/ardour_ui_startup.cc b/gtk2_ardour/ardour_ui_startup.cc
index e22db6cd6b..827212561b 100644
--- a/gtk2_ardour/ardour_ui_startup.cc
+++ b/gtk2_ardour/ardour_ui_startup.cc
@@ -866,7 +866,7 @@ ARDOUR_UI::load_from_application_api (const std::string& path)
 #else
 					"JACK",
 #endif
-					ARDOUR_COMMAND_LINE::backend_client_name, "")) {
+					ARDOUR_COMMAND_LINE::backend_session_id, "")) {
 			error << _("NSM: The JACK backend is mandatory and can not be loaded.") << endmsg;
 			return;
 		}
diff --git a/gtk2_ardour/engine_dialog.cc b/gtk2_ardour/engine_dialog.cc
index b7c80b9f09..44f0935aac 100644
--- a/gtk2_ardour/engine_dialog.cc
+++ b/gtk2_ardour/engine_dialog.cc
@@ -1024,7 +1024,7 @@ EngineControl::backend_changed ()
 	string                                  backend_name = backend_combo.get_active_text ();
 	std::shared_ptr<ARDOUR::AudioBackend> backend;
 
-	if (!(backend = ARDOUR::AudioEngine::instance ()->set_backend (backend_name, ARDOUR_COMMAND_LINE::backend_client_name, ""))) {
+	if (!(backend = ARDOUR::AudioEngine::instance ()->set_backend (backend_name, ARDOUR_COMMAND_LINE::backend_session_id, ""))) {
 		/* eh? setting the backend failed... how ? */
 		/* A: stale config contains a backend that does not exist in current build */
 		return;
@@ -2207,7 +2207,7 @@ EngineControl::set_current_state (const State& state)
 
 	std::shared_ptr<ARDOUR::AudioBackend> backend;
 
-	if (!(backend = ARDOUR::AudioEngine::instance ()->set_backend (state->backend, ARDOUR_COMMAND_LINE::backend_client_name, ""))) {
+	if (!(backend = ARDOUR::AudioEngine::instance ()->set_backend (state->backend, ARDOUR_COMMAND_LINE::backend_session_id, ""))) {
 		DEBUG_ECONTROL (string_compose ("Unable to set backend to %1", state->backend));
 		// this shouldn't happen as the invalid backend names should have been
 		// removed from the list of states.
diff --git a/gtk2_ardour/nsm.cc b/gtk2_ardour/nsm.cc
index 30e64455b8..57b69f9b78 100644
--- a/gtk2_ardour/nsm.cc
+++ b/gtk2_ardour/nsm.cc
@@ -49,7 +49,7 @@ NSM_Client::command_open(const char* name,
 {
 	int r = ERR_OK;
 
-	ARDOUR_COMMAND_LINE::backend_client_name = client_id;
+	ARDOUR_COMMAND_LINE::backend_session_id = client_id;
 	ARDOUR_COMMAND_LINE::session_name = "";
 
 	/* this appears asynchronous, but almost certainly is
diff --git a/gtk2_ardour/opts.cc b/gtk2_ardour/opts.cc
index 234381a249..14684b19d0 100644
--- a/gtk2_ardour/opts.cc
+++ b/gtk2_ardour/opts.cc
@@ -41,7 +41,7 @@
 using namespace std;
 
 string ARDOUR_COMMAND_LINE::session_name = "";
-string ARDOUR_COMMAND_LINE::backend_client_name = PBD::downcase(PROGRAM_NAME);
+string ARDOUR_COMMAND_LINE::backend_session_id = PBD::downcase(PROGRAM_NAME);
 bool  ARDOUR_COMMAND_LINE::show_key_actions = false;
 bool  ARDOUR_COMMAND_LINE::show_actions = false;
 bool ARDOUR_COMMAND_LINE::no_splash = false;
@@ -72,7 +72,7 @@ print_help (const char *execname)
 		<< _("  -A, --actions               Print all possible menu action names\n")
 		<< _("  -b, --bindings              Display all current key bindings\n")
 		<< _("  -B, --bypass-plugins        Bypass all plugins in an existing session\n")
-		<< _("  -c, --name <name>           Use a specific backend client name, default is ardour\n")
+		<< _("  -c, --name <session-id>     Specify audio backend client session id, default is ardour\n")
 		<< _("  -d, --disable-plugins       Disable all plugins (safe mode)\n")
 #ifndef NDEBUG
 		<< _("  -D, --debug <options>       Set debug flags. Use \"-D list\" to see available options\n")
@@ -218,7 +218,7 @@ ARDOUR_COMMAND_LINE::parse_opts (int argc, char *argv[])
 			break;
 
 		case 'c':
-			backend_client_name = optarg;
+			backend_session_id = optarg;
 			break;
 
 		case 'k':
diff --git a/gtk2_ardour/opts.h b/gtk2_ardour/opts.h
index 56e0b2c031..d9f58351a8 100644
--- a/gtk2_ardour/opts.h
+++ b/gtk2_ardour/opts.h
@@ -29,7 +29,7 @@ extern bool        show_key_actions;
 extern bool        show_actions;
 extern bool        no_splash;
 extern bool        just_version;
-extern std::string backend_client_name;
+extern std::string backend_session_id;
 extern bool        new_session;
 extern bool        try_hw_optimization;
 extern bool        no_connect_ports;
diff --git a/headless/load_session.cc b/headless/load_session.cc
index f921b83676..247b34bf83 100644
--- a/headless/load_session.cc
+++ b/headless/load_session.cc
@@ -48,7 +48,7 @@ using namespace PBD;
 
 static const char* localedir = LOCALEDIR;
 
-static string             backend_client_name;
+static string             backend_session_id;
 static CrossThreadChannel xthread (true);
 static TestReceiver       test_receiver;
 
@@ -72,7 +72,7 @@ load_session (string dir, string state)
 
 	AudioEngine* engine = AudioEngine::create ();
 
-	if (!engine->set_backend (backend_name, backend_client_name, "")) {
+	if (!engine->set_backend (backend_name, backend_session_id, "")) {
 		std::cerr << "Cannot set Audio/MIDI engine backend\n";
 		exit (EXIT_FAILURE);
 	}
@@ -172,7 +172,7 @@ main (int argc, char* argv[])
 
 	bool try_hw_optimization = true;
 
-	backend_client_name = PBD::downcase (std::string (PROGRAM_NAME));
+	backend_session_id = PBD::downcase (std::string (PROGRAM_NAME));
 
 	int c;
 	while ((c = getopt_long (argc, argv, optstring, longopts, (int*)0)) != EOF) {
@@ -191,7 +191,7 @@ main (int argc, char* argv[])
 				break;
 
 			case 'c':
-				backend_client_name = optarg;
+				backend_session_id = optarg;
 				break;
 
 			case 'B':
diff --git a/libs/ardour/ardour/audio_backend.h b/libs/ardour/ardour/audio_backend.h
index 85de704dd9..f337e21e92 100644
--- a/libs/ardour/ardour/audio_backend.h
+++ b/libs/ardour/ardour/audio_backend.h
@@ -44,11 +44,11 @@ namespace ARDOUR
 struct LIBARDOUR_API AudioBackendInfo {
 	const char* name;
 
-	/** Using arg1 and arg2, initialize this audiobackend.
+	/** Using arg1 and session_id, initialize this audiobackend.
 	 *
 	 * Returns zero on success, non-zero otherwise.
 	 */
-	int (*instantiate) (const std::string& arg1, const std::string& arg2);
+	int (*instantiate) (const std::string& arg1, const std::string& session_id);
 
 	/** Release all resources associated with this audiobackend */
 	int (*deinstantiate) (void);
diff --git a/libs/ardour/ardour/audioengine.h b/libs/ardour/ardour/audioengine.h
index a63913747c..c047c462a9 100644
--- a/libs/ardour/ardour/audioengine.h
+++ b/libs/ardour/ardour/audioengine.h
@@ -71,7 +71,7 @@ class LIBARDOUR_API AudioEngine : public PortManager, public SessionHandlePtr
 	int discover_backends();
 	std::vector<const AudioBackendInfo*> available_backends() const;
 	std::string current_backend_name () const;
-	std::shared_ptr<AudioBackend> set_backend (const std::string&, const std::string& arg1, const std::string& arg2);
+	std::shared_ptr<AudioBackend> set_backend (const std::string& name, const std::string& arg1, const std::string& session_id);
 	std::shared_ptr<AudioBackend> current_backend() const { return _backend; }
 	bool setup_required () const;
 	bool is_jack () const;
diff --git a/libs/ardour/audioengine.cc b/libs/ardour/audioengine.cc
index fd8cf65753..43a9a74bdb 100644
--- a/libs/ardour/audioengine.cc
+++ b/libs/ardour/audioengine.cc
@@ -1015,7 +1015,7 @@ AudioEngine::drop_backend ()
 }
 
 std::shared_ptr<AudioBackend>
-AudioEngine::set_backend (const std::string& name, const std::string& arg1, const std::string& arg2)
+AudioEngine::set_backend (const std::string& name, const std::string& arg1, const std::string& session_id)
 {
 	BackendMap::iterator b = _backends.find (name);
 
@@ -1026,7 +1026,7 @@ AudioEngine::set_backend (const std::string& name, const std::string& arg1, cons
 	drop_backend ();
 
 	try {
-		if (b->second->instantiate (arg1, arg2)) {
+		if (b->second->instantiate (arg1, session_id)) {
 			throw failed_constructor ();
 		}
 
diff --git a/libs/backends/alsa/alsa_audiobackend.cc b/libs/backends/alsa/alsa_audiobackend.cc
index 0234e47f9d..943ae0b23d 100644
--- a/libs/backends/alsa/alsa_audiobackend.cc
+++ b/libs/backends/alsa/alsa_audiobackend.cc
@@ -2181,7 +2181,7 @@ AlsaAudioBackend::AudioSlave::update_latencies (uint32_t play, uint32_t capt)
 static std::shared_ptr<AlsaAudioBackend> _instance;
 
 static std::shared_ptr<AudioBackend> backend_factory (AudioEngine& e);
-static int  instantiate (const std::string& arg1, const std::string& /* arg2 */);
+static int  instantiate (const std::string& arg1, const std::string& /* session_id */);
 static int  deinstantiate ();
 static bool already_configured ();
 static bool available ();
@@ -2205,7 +2205,7 @@ backend_factory (AudioEngine& e)
 }
 
 static int
-instantiate (const std::string& arg1, const std::string& /* arg2 */)
+instantiate (const std::string& arg1, const std::string& /* session_id */)
 {
 	s_instance_name = arg1;
 	return 0;
diff --git a/libs/backends/coreaudio/coreaudio_backend.cc b/libs/backends/coreaudio/coreaudio_backend.cc
index 0d14d24703..967660a6f8 100644
--- a/libs/backends/coreaudio/coreaudio_backend.cc
+++ b/libs/backends/coreaudio/coreaudio_backend.cc
@@ -1529,7 +1529,7 @@ CoreAudioBackend::hw_changed_callback ()
 static std::shared_ptr<CoreAudioBackend> _instance;
 
 static std::shared_ptr<AudioBackend> backend_factory (AudioEngine& e);
-static int instantiate (const std::string& arg1, const std::string& /* arg2 */);
+static int instantiate (const std::string& arg1, const std::string& /* session_id */);
 static int deinstantiate ();
 static bool already_configured ();
 static bool available ();
@@ -1553,7 +1553,7 @@ backend_factory (AudioEngine& e)
 }
 
 static int
-instantiate (const std::string& arg1, const std::string& /* arg2 */)
+instantiate (const std::string& arg1, const std::string& /* session_id */)
 {
 	s_instance_name = arg1;
 	return 0;
diff --git a/libs/backends/dummy/dummy_audiobackend.cc b/libs/backends/dummy/dummy_audiobackend.cc
index 6507d22a59..b153189b28 100644
--- a/libs/backends/dummy/dummy_audiobackend.cc
+++ b/libs/backends/dummy/dummy_audiobackend.cc
@@ -1016,7 +1016,7 @@ DummyAudioBackend::main_process_thread ()
 static std::shared_ptr<DummyAudioBackend> _instance;
 
 static std::shared_ptr<AudioBackend> backend_factory (AudioEngine& e);
-static int instantiate (const std::string& arg1, const std::string& /* arg2 */);
+static int instantiate (const std::string& arg1, const std::string& /* session_id */);
 static int deinstantiate ();
 static bool already_configured ();
 static bool available ();
@@ -1040,7 +1040,7 @@ backend_factory (AudioEngine& e)
 }
 
 static int
-instantiate (const std::string& arg1, const std::string& /* arg2 */)
+instantiate (const std::string& arg1, const std::string& /* session_id */)
 {
 	s_instance_name = arg1;
 	return 0;
diff --git a/libs/backends/jack/jack_api.cc b/libs/backends/jack/jack_api.cc
index 959e3e5838..5e437a4641 100644
--- a/libs/backends/jack/jack_api.cc
+++ b/libs/backends/jack/jack_api.cc
@@ -25,7 +25,7 @@ static std::shared_ptr<JACKAudioBackend> backend;
 static std::shared_ptr<JackConnection> jack_connection;
 
 static std::shared_ptr<AudioBackend> backend_factory (AudioEngine& ae);
-static int  instantiate (const std::string& arg1, const std::string& arg2);
+static int  instantiate (const std::string& arg1, const std::string& session_id);
 static int  deinstantiate ();
 static bool already_configured ();
 static bool available ();
@@ -58,10 +58,10 @@ backend_factory (AudioEngine& ae)
 }
 
 static int
-instantiate (const std::string& arg1, const std::string& arg2)
+instantiate (const std::string& arg1, const std::string& session_id)
 {
 	try {
-		jack_connection.reset (new JackConnection (arg1, arg2));
+		jack_connection.reset (new JackConnection (arg1, session_id));
 		backend.reset ();
 	} catch (...) {
 		return -1;
diff --git a/libs/backends/jack/jack_connection.cc b/libs/backends/jack/jack_connection.cc
index 207c4add79..ac1ee247a0 100644
--- a/libs/backends/jack/jack_connection.cc
+++ b/libs/backends/jack/jack_connection.cc
@@ -50,10 +50,10 @@ static void jack_halted_info_callback (jack_status_t code, const char* reason, v
 }
 
 
-JackConnection::JackConnection (const std::string& arg1, const std::string& arg2)
+JackConnection::JackConnection (const std::string& arg1, const std::string& session_id)
 	: _jack (0)
 	, _client_name (arg1)
-	, session_uuid (arg2)
+	, _session_id (session_id)
 	, _probed_buffer_size (0)
 	, _probed_sample_rate (0)
 {
@@ -116,7 +116,7 @@ JackConnection::open ()
 	get_jack_server_dir_paths (dirs);
 	set_path_env_for_jack_autostart (dirs);
 
-	if ((_jack = jack_client_open (_client_name.c_str(), JackSessionID, &status, session_uuid.c_str())) == 0) {
+	if ((_jack = jack_client_open (_client_name.c_str(), JackSessionID, &status, _session_id.c_str())) == 0) {
 		return -1;
 	}
 
diff --git a/libs/backends/jack/jack_connection.h b/libs/backends/jack/jack_connection.h
index b9aaab7aa8..164525665a 100644
--- a/libs/backends/jack/jack_connection.h
+++ b/libs/backends/jack/jack_connection.h
@@ -10,7 +10,7 @@ namespace ARDOUR {
 
 class JackConnection {
   public:
-    JackConnection (const std::string& client_name, const std::string& session_uuid);
+    JackConnection (const std::string& client_name, const std::string& session_id);
     ~JackConnection ();
 
     const std::string& client_name() const { return _client_name; }
@@ -35,7 +35,7 @@ class JackConnection {
   private:
     jack_client_t* volatile _jack;
     std::string _client_name;
-    std::string session_uuid;
+    std::string _session_id;
     static bool _in_control;
     uint32_t _probed_buffer_size; // when not in control
     uint32_t _probed_sample_rate; // when not in control
diff --git a/libs/backends/portaudio/portaudio_backend.cc b/libs/backends/portaudio/portaudio_backend.cc
index 5c0fb2ee0a..71b88e84bf 100644
--- a/libs/backends/portaudio/portaudio_backend.cc
+++ b/libs/backends/portaudio/portaudio_backend.cc
@@ -1793,7 +1793,7 @@ PortAudioBackend::process_port_connection_changes ()
 static std::shared_ptr<PortAudioBackend> _instance;
 
 static std::shared_ptr<AudioBackend> backend_factory (AudioEngine& e);
-static int instantiate (const std::string& arg1, const std::string& /* arg2 */);
+static int instantiate (const std::string& arg1, const std::string& /* session_id */);
 static int deinstantiate ();
 static bool already_configured ();
 static bool available ();
@@ -1817,7 +1817,7 @@ backend_factory (AudioEngine& e)
 }
 
 static int
-instantiate (const std::string& arg1, const std::string& /* arg2 */)
+instantiate (const std::string& arg1, const std::string& /* session_id */)
 {
 	s_instance_name = arg1;
 	return 0;
diff --git a/libs/backends/pulseaudio/pulseaudio_backend.cc b/libs/backends/pulseaudio/pulseaudio_backend.cc
index d3273eb4c9..de29b1a30f 100644
--- a/libs/backends/pulseaudio/pulseaudio_backend.cc
+++ b/libs/backends/pulseaudio/pulseaudio_backend.cc
@@ -1084,7 +1084,7 @@ PulseAudioBackend::main_process_thread ()
 static std::shared_ptr<PulseAudioBackend> _instance;
 
 static std::shared_ptr<AudioBackend> backend_factory (AudioEngine& e);
-static int instantiate (const std::string& arg1, const std::string& /* arg2 */);
+static int instantiate (const std::string& arg1, const std::string& /* session_id */);
 static int  deinstantiate ();
 static bool already_configured ();
 static bool available ();
@@ -1108,7 +1108,7 @@ backend_factory (AudioEngine& e)
 }
 
 static int
-instantiate (const std::string& arg1, const std::string& /* arg2 */)
+instantiate (const std::string& arg1, const std::string& /* session_id */)
 {
 	s_instance_name = arg1;
 	return 0;