Play musical notes in Swift Playground

Question

I am trying to play a short musical note sequence with a default sine wave as sound inside a Swift Playground. At a later point I'd like to replace the sound with a Soundfont but at the moment I'd be happy with just producing some sound.

I want this to be a midi like sequence with direct control over the notes, not something purely audio based. The AudioToolbox seems to provide what I am looking for but I have troubles fully understanding its usage. Here's what I am currently trying

import AudioToolbox  // Creating the sequence      var sequence:MusicSequence = nil var musicSequence = NewMusicSequence(&sequence)  // Creating a track  var track:MusicTrack = nil var musicTrack = MusicSequenceNewTrack(sequence, &track)  // Adding notes  var time = MusicTimeStamp(1.0) for index:UInt8 in 60...72 {     var note = MIDINoteMessage(channel: 0,                                note: index,                                velocity: 64,                                releaseVelocity: 0,                                duration: 1.0 )     musicTrack = MusicTrackNewMIDINoteEvent(track, time, &note)     time += 1 }  // Creating a player      var musicPlayer:MusicPlayer = nil var player = NewMusicPlayer(&musicPlayer)  player = MusicPlayerSetSequence(musicPlayer, sequence) player = MusicPlayerStart(musicPlayer) 

As you can imagine, there's no sound playing. I appreciate any ideas on how to have that sound sequence playing aloud.

Answer 1

You have to enable the asynchronous mode for the Playground.

Add this at the top (Xcode 7, Swift 2):

import XCPlayground XCPlaygroundPage.currentPage.needsIndefiniteExecution = true 

and your sequence will play.

The same for Xcode 8 (Swift 3):

import PlaygroundSupport PlaygroundPage.current.needsIndefiniteExecution = true 

Answer 2

Working MIDI example in a Swift Playground

import PlaygroundSupport import AudioToolbox  var sequence : MusicSequence? = nil var musicSequence = NewMusicSequence(&sequence)  var track : MusicTrack? = nil var musicTrack = MusicSequenceNewTrack(sequence!, &track)  // Adding notes  var time = MusicTimeStamp(1.0) for index:UInt8 in 60...72 { // C4 to C5     var note = MIDINoteMessage(channel: 0,                                note: index,                                velocity: 64,                                releaseVelocity: 0,                                duration: 1.0 )     musicTrack = MusicTrackNewMIDINoteEvent(track!, time, &note)     time += 1 }  // Creating a player  var musicPlayer : MusicPlayer? = nil var player = NewMusicPlayer(&musicPlayer)  player = MusicPlayerSetSequence(musicPlayer!, sequence) player = MusicPlayerStart(musicPlayer!)  PlaygroundPage.current.needsIndefiniteExecution = true 

Great MIDI reference page with a nice chart