SwiftSound

Experiements with simple sound synthesis in Swift.

Sounds are created by instantiating nodes (which might generate waveforms, perform arithmetic, etc.) and connecting them in a directed graph. Sound quality is not great (there's noticeable aliasing and glitching), but the purpose of this experiment is not exactly to create a world-class softsynth.

Examples

See AppDelegate.swift for some simple examples.

The following creates a sine wave with a frequency of 440 Hz and an amplitude of 1:

var osc = SineWave(440.Hz)

Any node can be converted to WAV NSData or played for a given duration:

osc.toWAV(44100.Hz, duration: 2.sec).writeToURL(url, atomically: true)
osc.play(2.sec) // 44100 sample rate is implied if not specified

Musical notes can be referenced with a shorthand notation:

var middleC = SineWave(C-4)
var cSharp  = SineWave(C+4)

Chords can be created by adding oscillators together:

var cMajor = SineWave(C-4) + SineWave(E-4) + SineWave(G-4)

Multiplying an oscillator by a low-frequency oscillator produces amplitude modulation.

var am = SawtoothWave(A-4) * TriangleWave(2.Hz)

Multiplying an oscillator by another audio-frequency oscillator produces ring modulation.

var ringMod = SquareWave(A-2) * TriangleWave(700.Hz)

Using one oscillator as the frequency input of another produces frequency modulation. (Also note that the amplitude of any node can be scaled by multiplying it by a constant.)

var siren = TriangleWave(1000.Hz + 400*SineWave(1.Hz))

Notes can be transposed by semitones or octaves:

let majorSeventhChord = {
  SineWave($0) + 
  SineWave($0+4.semitones) + 
  SineWave($0+7.semitones) +
  SineWave($0+11.semitones)
}
let cMaj7 = majorSeventhChord(C-4)

The Noise node generates a constant stream of white noise. It can be tuned/quantized using the SampleAndHold node.

let eightBitNoise = SampleAndHold(500.Hz, input: Noise())
let beepsAndBoops = SquareWave(440.Hz + 100*SampleAndHold(10.Hz, input: Noise()))

Piecewise nodes can be used to create custom waveforms and to play arpeggios and tunes.

let loFiTriangle = Piecewise(C-4, values: [0, 0.5, 1, 0.5, 0, -0.5, -1, -0.5])
let arp = SquareWave(Piecewise(2.Hz, values: [C-4, E-4, G-4]))

Notes

This is my first significant venture into Swift. I haven't learned all the idioms yet; feel free to submit a pull request correcting anything that looks weird.

I'm on Twitter: @autorelease

s7ash/SwiftSound

SwiftSound

Examples

Notes