diff --git a/Makefile b/Makefile
index 9505770..90083c1 100644
--- a/Makefile
+++ b/Makefile
@@ -13,6 +13,9 @@ install: all
 	SUBDIR=`racket -e "(display (format \"~a-~a\" (system-type 'os*) (system-type 'arch)))"`; \
 	FILES=`ls build/*.dll` 2>/dev/null; if [ "$$FILES" != "" ]; then cp $$FILES lib/$$SUBDIR; fi
 
+test: install
+	cp lib/linux-x86_64/*.so ~/.local/share/racket/racket-sound-lib/linux-x86_64
+
 zip: install
 	SUBDIR=`racket -e "(display (format \"~a-~a\" (system-type 'os*) (system-type 'arch)))"`; \
 	(cd lib; zip -y -r -9 $$SUBDIR.zip $$SUBDIR)
diff --git a/ao-play-async/ao_playasync.c b/ao-play-async/ao_playasync.c
index fdb4e7d..dff68b5 100644
--- a/ao-play-async/ao_playasync.c
+++ b/ao-play-async/ao_playasync.c
@@ -16,6 +16,7 @@
 
 #ifdef USE_PTHREADS
   #include <pthread.h>
+  #include <semaphore.h>
   #define MUTEX_LOCK(m) pthread_mutex_lock(&m)
   #define MUTEX_UNLOCK(m) pthread_mutex_unlock(&m)
 #endif
@@ -55,21 +56,26 @@ typedef int(*ao_play_func_t)(void *, char *, uint32_t);
 typedef struct {
     Queue_t        *play_queue;
     Queue_t        *last_frame;
+    sem_t           queue_sem;
+
+    int             paused;
+
     ao_device      *ao_device;
 #ifdef USE_WINDOWS_THREADS
     HANDLE          mutex;
+    HANDLE          pause_mutex;
     HANDLE          thread;
     DWORD           thread_id;
 #endif
 #ifdef USE_PTHREADS
     pthread_mutex_t mutex;
+    pthread_mutex_t pause_mutex;
     pthread_t       thread;
 #endif
     double          at_second;
     double          music_duration;
     ao_play_func_t  ao_play_f;
     int             buf_size;
-    int             paused;
 } AO_Handle;
 
 //static int(*ao_play)(void *device, char *samples, uint32_t n) = NULL;
@@ -83,6 +89,8 @@ static Queue_t *front(AO_Handle *h)
 
 static Queue_t *get(AO_Handle *h)
 {
+    sem_wait(&h->queue_sem);
+    MUTEX_LOCK(h->mutex);
     assert(h->play_queue != NULL);
     Queue_t *q = h->play_queue;
     h->play_queue = h->play_queue->next;
@@ -92,11 +100,13 @@ static Queue_t *get(AO_Handle *h)
         h->play_queue->prev = NULL;
     }
     h->buf_size -= q->buflen;
+    MUTEX_UNLOCK(h->mutex);
     return q;
 }
 
 static void add(AO_Handle *h, Queue_t *elem)
 {
+    MUTEX_LOCK(h->mutex);
     if (h->last_frame == NULL) {
         h->play_queue = elem;
         elem->next = NULL;
@@ -109,6 +119,8 @@ static void add(AO_Handle *h, Queue_t *elem)
         h->last_frame = elem;
     }
     h->buf_size += elem->buflen;
+    MUTEX_UNLOCK(h->mutex);
+    sem_post(&h->queue_sem);
 }
 
 static Queue_t *new_elem(int command, double at_second, double music_duration, int buf_len, void *buf)
@@ -126,7 +138,7 @@ static Queue_t *new_elem(int command, double at_second, double music_duration, i
     q->music_duration = music_duration;
     q->buf = new_buf;
     q->buflen = buf_len;
-    q->command = command;
+    q->command = (Command_t) command;
     q->next = NULL;
     q->prev = NULL;
     return q;
@@ -160,27 +172,22 @@ static DWORD run(LPVOID arg)
     int go_on = (1 == 1);
 
     while(go_on) {
-        MUTEX_LOCK(handle->mutex);
-        int has_frames = (!handle->paused) && (handle->play_queue != NULL);
+        MUTEX_LOCK(handle->pause_mutex);
+        MUTEX_UNLOCK(handle->pause_mutex);
 
-        if (has_frames) {
-            Queue_t *q = get(handle);
-            handle->at_second = q->at_second;
-            handle->music_duration = q->music_duration;
-            MUTEX_UNLOCK(handle->mutex);
+        Queue_t *q = get(handle);
 
-            if (q->command == STOP) {
-                go_on = (1 == 0);
-            } else {
-                //fprintf(stderr, "playing buf at %lf\n", handle->at_second);
-                handle->ao_play_f(handle->ao_device, q->buf, q->buflen);
-            }
+        handle->at_second = q->at_second;
+        handle->music_duration = q->music_duration;
 
-            del_elem(q);
+        if (q->command == STOP) {
+            go_on = (1 == 0);
         } else {
-            MUTEX_UNLOCK(handle->mutex);
-            sleep_ms(5);   // sleep for 5ms
+            //fprintf(stderr, "playing buf at %lf\n", handle->at_second);
+            handle->ao_play_f(handle->ao_device, (char *) q->buf, q->buflen);
         }
+
+        del_elem(q);
     }
 
 #ifdef USE_PTHREADS
@@ -207,23 +214,33 @@ void *ao_create_async(void *ao_device_yeah, void *ao_play_f)
     handle->last_frame = NULL;
     handle->at_second = -1;
 
-    handle->ao_play_f = ao_play_f;
+    handle->ao_play_f = (ao_play_func_t) ao_play_f;
     handle->buf_size = 0;
+
     handle->paused = (1 == 0);
 
 #ifdef USE_PTHREADS
+    pthread_mutex_t p = PTHREAD_MUTEX_INITIALIZER;
+    handle->pause_mutex = p;
     pthread_mutex_t m = PTHREAD_MUTEX_INITIALIZER;
     handle->mutex = m;
     pthread_create(&handle->thread, NULL, run, handle);
+    sem_init(&handle->queue_sem, 0, 0);
 #endif
 
 #ifdef USE_WINDOWS_THREADS
     handle->mutex = CreateMutex(NULL,              // default security attributes
                                 FALSE,             // initially not owned
                                 NULL);
+    handle->pause_mutex = CreateMutex(NULL,              // default security attributes
+                                FALSE,             // initially not owned
+                                NULL);
     handle->thread = CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE) run, handle, 0, &handle->thread_id);
+    // TODO Windows Semaphores!
 #endif
 
+    MUTEX_UNLOCK(handle->pause_mutex);
+
     return (void *) handle;
 }
 
@@ -231,11 +248,9 @@ void ao_stop_async(void *ao_handle)
 {
     AO_Handle *h = (AO_Handle *) ao_handle;
 
-    MUTEX_LOCK(h->mutex);
     clear(h);
     Queue_t *q = new_elem(STOP, 0.0, 0.0, 0, NULL);
     add(h, q);
-    MUTEX_UNLOCK(h->mutex);
 
 #ifdef USE_PTHREADS
     void *retval;
@@ -375,17 +390,13 @@ void ao_play_async(void *ao_handle, double at_second, double music_duration, int
       break;
     }
 
-    MUTEX_LOCK(h->mutex);
     add(h, q);
-    MUTEX_UNLOCK(h->mutex);
 }
 
 void ao_clear_async(void *ao_handle)
 {
     AO_Handle *h = (AO_Handle *) ao_handle;
-    MUTEX_LOCK(h->mutex);
     clear(h);
-    MUTEX_UNLOCK(h->mutex);
 }
 
 double ao_is_at_second_async(void *ao_handle)
@@ -419,7 +430,19 @@ void ao_pause_async(void *ao_handle, int paused)
 {
     AO_Handle *h = (AO_Handle *) ao_handle;
     MUTEX_LOCK(h->mutex);
-    h->paused = paused;
+
+    if (h->paused) {
+      if (!paused) {
+        h->paused = paused;
+        MUTEX_UNLOCK(h->pause_mutex);
+      }
+    } else {
+      if (paused) {
+        h->paused = paused;
+        MUTEX_LOCK(h->pause_mutex);
+      }
+    }
+
     MUTEX_UNLOCK(h->mutex);
 }
 
diff --git a/lib/linux-x86_64.zip b/lib/linux-x86_64.zip
index 01e7efd..819d041 100644
Binary files a/lib/linux-x86_64.zip and b/lib/linux-x86_64.zip differ