     func updateButtons() {
         let buttons: [AKButton] = [button1, button2, button3, button4]
         for i in 0 ..< buttons.count {
-            if sequencer.avTracks[i + 1].destinationAudioUnit == bellSampler.samplerUnit {
+            if sequencer.tracks[i + 1].destinationAudioUnit == bell.samplerUnit {
                 buttons[i].title = "Track \(i + 1): Bell"
                 buttons[i].color = AKColor.red
 

        addSubview(button4)
    }

    func toggleTrack(trackNumber: Int) {
        sequencer.stop()
        if sequencer.avTracks[trackNumber].destinationAudioUnit == bellSampler.samplerUnit {
            sequencer.avTracks[trackNumber].destinationAudioUnit = fmPianoSampler.samplerUnit
        } else {
            sequencer.avTracks[trackNumber].destinationAudioUnit = bellSampler.samplerUnit
        }
        updateButtons()
    }

import AudioKit

//: Create some samplers, load different sounds, and connect it to a mixer and the output
var piano = AKSampler()
try piano.loadWav("Samples/FM Piano")

var bell = AKSampler()
try bell.loadWav("Samples/Bell")

var mixer = AKMixer(piano, bell)

let reverb = AKCostelloReverb(mixer)

