diff --git a/sys/dev/sound/midi/midi.h b/sys/dev/sound/midi/midi.h
--- a/sys/dev/sound/midi/midi.h
+++ b/sys/dev/sound/midi/midi.h
@@ -41,6 +41,8 @@
 
 #define MIDI_TYPE unsigned char
 
+extern struct sx midistat_lock;
+
 struct snd_midi;
 
 struct snd_midi *
@@ -50,8 +52,10 @@
 int	midi_in(struct snd_midi *_m, MIDI_TYPE *_buf, int _size);
 
 kobj_t	midimapper_addseq(void *arg1, int *unit, void **cookie);
+int	midimapper_open_locked(void *arg1, void **cookie);
 int	midimapper_open(void *arg1, void **cookie);
 int	midimapper_close(void *arg1, void *cookie);
+kobj_t	midimapper_fetch_synth_locked(void *arg, void *cookie, int unit);
 kobj_t	midimapper_fetch_synth(void *arg, void *cookie, int unit);
 
 #endif
diff --git a/sys/dev/sound/midi/midi.c b/sys/dev/sound/midi/midi.c
--- a/sys/dev/sound/midi/midi.c
+++ b/sys/dev/sound/midi/midi.c
@@ -181,7 +181,8 @@
  * /dev/midistat variables and declarations, protected by midistat_lock
  */
 
-static struct sx midistat_lock;
+struct sx midistat_lock;
+
 static int      midistat_isopen = 0;
 static struct sbuf midistat_sbuf;
 static struct cdev *midistat_dev;
@@ -1470,16 +1471,28 @@
 }
 
 int
-midimapper_open(void *arg1, void **cookie)
+midimapper_open_locked(void *arg1, void **cookie)
 {
 	int retval = 0;
 	struct snd_midi *m;
 
-	sx_xlock(&midistat_lock);
+	sx_assert(&midistat_lock, SX_XLOCKED);
 	TAILQ_FOREACH(m, &midi_devs, link) {
 		retval++;
 	}
+
+	return retval;
+}
+
+int
+midimapper_open(void *arg1, void **cookie)
+{
+	int retval;
+
+	sx_xlock(&midistat_lock);
+	retval = midimapper_open_locked(arg1, cookie);
 	sx_xunlock(&midistat_lock);
+
 	return retval;
 }
 
@@ -1490,22 +1503,32 @@
 }
 
 kobj_t
-midimapper_fetch_synth(void *arg, void *cookie, int unit)
+midimapper_fetch_synth_locked(void *arg, void *cookie, int unit)
 {
 	struct snd_midi *m;
 	int retval = 0;
 
-	sx_xlock(&midistat_lock);
+	sx_assert(&midistat_lock, SX_XLOCKED);
 	TAILQ_FOREACH(m, &midi_devs, link) {
-		if (unit == retval) {
-			sx_xunlock(&midistat_lock);
+		if (unit == retval)
 			return (kobj_t)m->synth;
-		}
 		retval++;
 	}
-	sx_xunlock(&midistat_lock);
+
 	return NULL;
 }
 
+kobj_t
+midimapper_fetch_synth(void *arg, void *cookie, int unit)
+{
+	kobj_t synth;
+
+	sx_xlock(&midistat_lock);
+	synth = midimapper_fetch_synth_locked(arg, cookie, unit);
+	sx_xunlock(&midistat_lock);
+
+	return synth;
+}
+
 DEV_MODULE(midi, midi_modevent, NULL);
 MODULE_VERSION(midi, 1);
diff --git a/sys/dev/sound/midi/sequencer.c b/sys/dev/sound/midi/sequencer.c
--- a/sys/dev/sound/midi/sequencer.c
+++ b/sys/dev/sound/midi/sequencer.c
@@ -64,6 +64,7 @@
 #include <sys/kthread.h>
 #include <sys/unistd.h>
 #include <sys/selinfo.h>
+#include <sys/sx.h>
 
 #ifdef HAVE_KERNEL_OPTION_HEADERS
 #include "opt_snd.h"
@@ -751,6 +752,7 @@
 	 * Mark this device busy.
 	 */
 
+	sx_xlock(&midistat_lock);
 	mtx_lock(&scp->seq_lock);
 	if (scp->busy) {
 		mtx_unlock(&scp->seq_lock);
@@ -768,14 +770,15 @@
 	 * Enumerate the available midi devices
 	 */
 	scp->midi_number = 0;
-	scp->maxunits = midimapper_open(scp->mapper, &scp->mapper_cookie);
+	scp->maxunits = midimapper_open_locked(scp->mapper, &scp->mapper_cookie);
 
 	if (scp->maxunits == 0)
 		SEQ_DEBUG(2, printf("seq_open: no midi devices\n"));
 
 	for (i = 0; i < scp->maxunits; i++) {
 		scp->midis[scp->midi_number] =
-		    midimapper_fetch_synth(scp->mapper, scp->mapper_cookie, i);
+		    midimapper_fetch_synth_locked(scp->mapper,
+		    scp->mapper_cookie, i);
 		if (scp->midis[scp->midi_number]) {
 			if (SYNTH_OPEN(scp->midis[scp->midi_number], scp,
 				scp->fflags) != 0)
@@ -803,6 +806,7 @@
 
 	scp->busy = 1;
 	mtx_unlock(&scp->seq_lock);
+	sx_xunlock(&midistat_lock);
 
 	SEQ_DEBUG(2, printf("seq_open: opened, mode %s.\n",
 	    scp->music ? "music" : "sequencer"));