Chapter 3 my solution for side quest

Code Block 
func performance(owner: Assessable) {
		let toneOutput = ToneOutput()
		let bassToneOutput = ToneOutput()
		let qPitches:[Pitch] = [.e3, .e3, .f3, .g3, .g3, .f3, .e3, .d3, .c3, .c3, .d3, .e3, .e3, .d3]
		let hPitches:[Pitch] = [.d3]
		let notes: [Note] = qPitches.map{Note.quarter($0)} + hPitches.map{Note.half($0)}
		var pitches = [Pitch]()
		for note in notes {
				pitches.append(contentsOf: note.subdivide())
		}
		var index = 0
		let interval = TimeInterval(Note.shortestSupportedNoteLength * 0.5)
		Timer.scheduledTimer(withTimeInterval: interval, repeats: true) { timer in
				guard index < pitches.count else {
						toneOutput.stopTones()
						bassToneOutput.stopTones()
						timer.invalidate()
						owner.endPerformance()
						return
				}
				
				toneOutput.play(tone: Tone(pitch: pitches[index].frequency, volume: 0.3))
				bassToneOutput.play(tone: Tone(pitch: pitches[index].bassFrequency, volume: 0.3))
				index += 1
		}
				// Second timer but it won’t with the first timer.
//			Timer.scheduledTimer(withTimeInterval: interval, repeats: true) { timer in
//					guard index < pitches.count else {
//							bassToneOutput.stopTones()
//							timer.invalidate()
//							owner.endPerformance()
//							return
//					}
//					
//					bassToneOutput.play(tone: Tone(pitch: pitches[index].bassFrequency, volume: 0.3))
//					//index += 1
//			}
		
		owner.endPerformance()
}

Code Block language
public var bassFrequency: Double {
				return self.rawValue/2.0
 }