fix metronome playback (was affected by drums playback fix)

src/Playback/PlaybackManager.ts

@@ -47,6 +47,7 @@ export class PlaybackManager implements IPlaybackParametersListener {
         this.listeners.push(listener);
     }
     private readonly percussionChannel: number = 10; // this is a definition of the midi interface (cannot be changed)
+    private readonly metronomeChannel: number = 9;
     private messageViewer: IMessageViewer;
     private audioMetronomePlayer: IAudioMetronomePlayer;
     private audioPlayer: IAudioPlayer<any>;
@@ -70,8 +71,8 @@ export class PlaybackManager implements IPlaybackParametersListener {
     private freeMidiChannels: number[] = [];
     private notesToStop: Dictionary<Fraction, ChannelNote[]> = new Dictionary<Fraction, ChannelNote[]>();
 
-    private metronomeNote: ChannelNote = new ChannelNote(88, this.percussionChannel);
-    private metronomeNoteFirstBeat: ChannelNote = new ChannelNote(64, this.percussionChannel);
+    private metronomeNote: ChannelNote = new ChannelNote(88, this.metronomeChannel);
+    private metronomeNoteFirstBeat: ChannelNote = new ChannelNote(64, this.metronomeChannel);
 
 
     private currentMeasure: SourceMeasure = undefined;
@@ -284,6 +285,9 @@ export class PlaybackManager implements IPlaybackParametersListener {
                 this.audioPlayer.open(uniqueMidiInstruments, 16);
                 // set drums:
                 this.audioPlayer.setSound(this.percussionChannel, MidiInstrument.Percussion);
+                // TODO might be unnecessary to use another channel,
+                //   if we find sounds in the percussion channel that match these for metronomeNote (88 and 64 for woodblock):
+                this.audioPlayer.setSound(this.metronomeChannel, MidiInstrument.Woodblock);
             }
 
             this.currentReferenceBPM = this.sheetStartBPM = musicSheet.getExpressionsStartTempoInBPM();