diff --git a/jackdriver.c b/jackdriver.c
index 9db4d52..aef4d87 100644
--- a/jackdriver.c
+++ b/jackdriver.c
@@ -150,12 +150,24 @@ process_midi_input(JACK_SEQ* seq,jack_nframes_t nframes)
     jack_midi_event_t event;
 
     void *port_buffer = jack_port_get_buffer(seq->input_port[k], nframes);
+    // this is used for direct pass-through of system messages
+    void *out_buffer = seq->passthrough && k < seq->n_out?
+      jack_port_get_buffer(seq->output_port[k], nframes):0;
     if (port_buffer == NULL)
     {
       fprintf(stderr, "jack_port_get_buffer failed, cannot receive anything.\n");
       return;
     }
 
+    if (out_buffer)
+    {
+#ifdef JACK_MIDI_NEEDS_NFRAMES
+      jack_midi_clear_buffer(out_buffer, nframes);
+#else
+      jack_midi_clear_buffer(out_buffer);
+#endif
+    }
+
 #ifdef JACK_MIDI_NEEDS_NFRAMES
     events = jack_midi_get_event_count(port_buffer, nframes);
 #else
@@ -174,7 +186,7 @@ process_midi_input(JACK_SEQ* seq,jack_nframes_t nframes)
       {
 	//successful event get
 
-	if (event.size <= 3 && event.size >= 1)
+	if (event.size <= 3 && event.size >= 1 && event.buffer[0] < 0xf0)
 	{
 	  //not sysex or something
 
@@ -185,6 +197,16 @@ process_midi_input(JACK_SEQ* seq,jack_nframes_t nframes)
 	  memcpy(rev.data, event.buffer, rev.len);
 	  queue_message(seq->ringbuffer_in[k],&rev);
 	}
+	else if (out_buffer && event.size >= 1 && event.buffer[0] >= 0xf0)
+	{
+	  // direct pass-through of system messages
+#ifdef JACK_MIDI_NEEDS_NFRAMES
+	  uint8_t *buffer = jack_midi_event_reserve(out_buffer, event.time, event.size, nframes);
+#else
+	  uint8_t *buffer = jack_midi_event_reserve(out_buffer, event.time, event.size);
+#endif
+	  if (buffer) memcpy(buffer, event.buffer, event.size);
+	}
       }
 
     }
@@ -211,11 +233,14 @@ process_midi_output(JACK_SEQ* seq,jack_nframes_t nframes)
       return;
     }
 
+    if (!seq->passthrough)
+    {
 #ifdef JACK_MIDI_NEEDS_NFRAMES
-    jack_midi_clear_buffer(port_buffer, nframes);
+      jack_midi_clear_buffer(port_buffer, nframes);
 #else
-    jack_midi_clear_buffer(port_buffer);
+      jack_midi_clear_buffer(port_buffer);
 #endif
+    }
 
     while (jack_ringbuffer_read_space(seq->ringbuffer_out[k]))
     {
diff --git a/jackdriver.h b/jackdriver.h
index 1fbec0f..4a94c86 100644
--- a/jackdriver.h
+++ b/jackdriver.h
@@ -11,8 +11,7 @@ typedef struct _jseq
   jack_client_t	*jack_client;
   jack_port_t	**output_port;
   jack_port_t	**input_port;
-  uint8_t n_in;
-  uint8_t n_out;
+  uint8_t n_in, n_out, passthrough;
 } JACK_SEQ;
 
 extern int jack_quit;
diff --git a/midizap.c b/midizap.c
index 175398f..d29e05c 100644
--- a/midizap.c
+++ b/midizap.c
@@ -20,7 +20,7 @@ typedef struct input_event EV;
 Display *display;
 
 JACK_SEQ seq;
-int jack_num_outputs = 0, debug_jack = 0;
+int jack_num_outputs = 0, debug_jack = 0, passthrough = 0;
 int shift = 0;
 
 void
@@ -1489,14 +1489,15 @@ handle_event(uint8_t *msg, uint8_t portno, int depth, int recursive)
 
 void help(char *progname)
 {
-  fprintf(stderr, "Usage: %s [-h] [-k] [-o[n]] [-j name] [-P[prio]] [-r rcfile] [-d[rskmj]]\n", progname);
+  fprintf(stderr, "Usage: %s [-hks] [-d[rskmj]] [-o[n]] [-j name] [-P[prio]] [-r rcfile]\n", progname);
   fprintf(stderr, "-h print this message\n");
+  fprintf(stderr, "-d debug (r = regex, s = strokes, k = keys, m = midi, j = jack; default: all)\n");
+  fprintf(stderr, "-j jack client name (default: midizap)\n");
   fprintf(stderr, "-k keep track of key status (ignore double notes)\n");
   fprintf(stderr, "-o set number of MIDI output ports (0-2, default: 1)\n");
-  fprintf(stderr, "-j jack client name (default: midizap)\n");
   fprintf(stderr, "-P set real-time priority (default: 90)\n");
   fprintf(stderr, "-r config file name (default: MIDIZAP_CONFIG_FILE variable or ~/.midizaprc)\n");
-  fprintf(stderr, "-d debug (r = regex, s = strokes, k = keys, m = midi, j = jack; default: all)\n");
+  fprintf(stderr, "-s pass-through of system messages\n");
 }
 
 uint8_t quit = 0;
@@ -1573,7 +1574,7 @@ main(int argc, char **argv)
   // Start recording the command line to be passed to Jack session management.
   add_command(argv[0], 0);
 
-  while ((opt = getopt(argc, argv, "hko::d::j:r:P::")) != -1) {
+  while ((opt = getopt(argc, argv, "hko::d::j:r:P::s")) != -1) {
     switch (opt) {
     case 'h':
       help(argv[0]);
@@ -1662,6 +1663,10 @@ main(int argc, char **argv)
 	exit(1);
       }
       break;
+    case 's':
+      passthrough = 1;
+      add_command("-s", 1);
+      break;
     default:
       fprintf(stderr, "Try -h for help.\n");
       exit(1);
@@ -1687,6 +1692,7 @@ main(int argc, char **argv)
   seq.client_name = jack_client_name;
   seq.n_in = jack_num_outputs>1?jack_num_outputs:1;
   seq.n_out = jack_num_outputs>0?jack_num_outputs:0;
+  seq.passthrough = jack_num_outputs>0?passthrough:0;
   if (!init_jack(&seq, debug_jack)) {
     exit(1);
   }