diff --git a/services/audioflinger/FastMixer.h b/services/audioflinger/FastMixer.h
index c31d476..97ab635 100644
--- a/services/audioflinger/FastMixer.h
+++ b/services/audioflinger/FastMixer.h
@@ -59,6 +59,14 @@
     virtual void onStateChange();
     virtual void onWork();
 
+    enum Reason {
+        REASON_REMOVE,
+        REASON_ADD,
+        REASON_MODIFY,
+    };
+    // called when a fast track of index has been removed, added, or modified
+    void updateMixerTrack(int index, Reason reason);
+
     // FIXME these former local variables need comments
     static const FastMixerState sInitial;