         parameterTree.implementorValueProvider = { param in
             if param == self.volumeControl {
                 return AUValue(self.volume.gain)
+            }
+            if param == self.filterControl {
+                return AUValue(self.filter.cutoffFrequency)
             }
             // if param == other values here...
             return 0

        name: "Volume",
        address: 0,
        range: 0.0 ... 1.0,
        unit: .generic,
        flags: .default)



class Conductor {
    var osc = AKOscillatorBank(waveform: AKTable(.square))
    var filter = AKMoogLadder()
    var volume = AKBooster()
    var parameterTree: AUParameterTree
    let volumeControl = AUParameter(
