Index: apps/pcmbuf.c
===================================================================
--- apps/pcmbuf.c	(revision 19401)
+++ apps/pcmbuf.c	(working copy)
@@ -972,10 +972,18 @@
     /* Find the insertion point and set bufstart to the start of it */
     if (mix)
     {
-        /* Get the next chunk */
-        char *pcmbuf_mix_buf = pcmbuf_read->link->addr;
-        /* Give 1/8s clearance. */
-        bufstart = (int16_t *)&pcmbuf_mix_buf[NATIVE_FREQUENCY * 4 / 8];
+        /* Get the currently playing chunk */
+        bufstart = (int16_t*)pcm_play_dma_get_peak_buffer(&i);
+
+        if (!bufstart)
+            return; /* If this function isn't implemented, no beepeth */
+
+        /* Give 5ms clearance. */    
+        bufstart += NATIVE_FREQUENCY * 4 / 200;
+        /* NOTE: On some targets using hardware DMA, cache range flushing may
+         * be required or the writes may not be picked up by the controller.
+         * An incremental flush should be done periodically during the mixdown.
+         */
     }
     else
     {
@@ -1000,11 +1008,15 @@
         phase += step;
     }
 
+    pcm_play_lock();
+
     /* Kick off playback if required */
     if (!pcm_is_playing())
     {
         pcm_play_data(NULL, (unsigned char *)bufstart, samples * 4);
     }
+
+    pcm_play_unlock();
 }
 #endif /* HAVE_HARDWARE_BEEP */