diff --git a/src/sound/i_musicinterns.h b/src/sound/i_musicinterns.h
index d10c941a29..82ce9c07fd 100644
--- a/src/sound/i_musicinterns.h
+++ b/src/sound/i_musicinterns.h
@@ -248,6 +248,7 @@ public:
 	void Stop ();
 	bool IsPlaying ();
 	bool IsValid () const { return CommandLine.Len() > 0; }
+	void SetVolume (float volume);
 
 protected:
 	void PrepTimidity ();