 
             guard let auAudioUnit = targetNode?.avAudioNode.auAudioUnit else { return }
 
+            renderObserver = observer
             if renderObserverToken == nil {
                 renderObserverToken = auAudioUnit.token(byAddingRenderObserver: observer)
             }

    }

    /// Sequence on this track
    public var sequence = NoteEventSequence() { didSet { updateSequence() }}

    /// Remove the notes in the track
    public func clear() {

    }

    private var renderObserverToken: Int?
    public var renderObserver: AURenderObserver?

    private func updateSequence() {
        guard let block = targetNode?.avAudioNode.auAudioUnit.scheduleMIDIEventBlock else {
