Shepard Tone Chuck

//--------------------------------------------------------------------
// name: shepard-wav-func.ck
// desc: Shepard–Risset illusion from a WAV sample, ascending or descending
//--------------------------------------------------------------------

// Shepard-tone generator as a sporkable function
fun void shepardTone(string samplePath, float direction)
{
    // direction: positive = ascending, negative = descending
    .004 / 16.0 * direction => float INC;
    1::ms => dur T;

    // Gaussian parameters
    66 => float MU;
    42 => float SIGMA;
    1 / Math.gauss(MU, MU, SIGMA) => float SCALE;

    // MIDI pitch values across several octaves
    [ 12.0, 24, 36, 48, 60, 72, 84, 96, 108 ] @=> float pitches[];
    pitches.size() => int N;

    // output gain
    Gain gain => dac;
    (1.0/N)*(0.5*N) => gain.gain;

    // sample players
    SndBuf bufs[N];

    // load and connect
    for (int i; i < N; i++)
    {
        samplePath => bufs[i].read;
        bufs[i] => gain;
        bufs[i].loop(1);
        0 => bufs[i].pos;
    }

    // reference frequency for rate calculation
    440.0 => float baseFreq;

    // continuous illusion loop
    while (true)
    {
        for (int i; i < N; i++)
        {
            pitches[i] => Std.mtof => float freq;
            freq / baseFreq => bufs[i].rate;

            Math.gauss(pitches[i], MU, SIGMA) * SCALE => float intensity;
            intensity * 96 => Math.dbtorms => bufs[i].gain;

            INC +=> pitches[i];

            if (pitches[i] > 120) 108 -=> pitches[i];
            else if (pitches[i] < 12) 108 +=> pitches[i];
        }

        T => now;
    }
}

//--------------------------------------------------------------------
// Example usage
//--------------------------------------------------------------------

// ascending illusion
spork ~ shepardTone("C:/Users/juliu/Downloads/VCR noise no click.wav",  1.0);

// descending illusion (starts a second later)
1::second => now;
//spork ~ shepardTone("C:/Users/juliu/Downloads/VCR noise no click.wav", -1.0);

// run forever
while (true) 1::second => now;