Shepard tone with muzikilo.js

shepard.js

// https://github.com/anuejn/muzikilo.js

const {sin, PI, round, pow, abs, floor, exp} = Math
this.t += 1/44100

const sine = (name, f) => {
    let phi = this[name] += 1/44100 * 2 * PI * f * saw(name+10000,f*0.5)
    this[name] %= 2*PI
    return sin(phi)
}
const saw = (name, f) => {
    let phi = this[name] += 1/44100 * f
    this[name] %= 1
    return phi
}

const len = 40 * knobs.seconds + 1
const octaves = 4 * knobs.octaves
const minFreq = knobs.minFreq * 440
const tones = Math.floor(9 * knobs.tones) + 1

const tone = (name, t) => {
    let freq = minFreq + (t % len) / len * 440*octaves 
    
    // downwards:
    //freq = minFreq + 440 * octaves - freq
    
    let vol = abs(((t-len/2) % len) / len - 0.5)
    vol = pow(vol, 3)
    //return saw(name, freq) * vol
    return sine(name, freq) * vol
}

let v = 0;
for (let i = 0; i < tones; i+=1) {
    let off = len / tones * i
    v += tone(i, this.t+off)
}
return v * 2 * knobs.volume

Nice :)

One possible performance enhancement is to replace this[name] with this[number]. Adding two numbers is much faster than concatenating two strings, plus it doesn't overload the garbage collector.

const Sine = 0
const Saw = 1
const Tone = 2
function name(type, index) {
    return 16 * index + type
}

// And then:
this[name(Sine, 14)] = …