Note Envelope
An Envelope is a series of fades, defined
as time / value pairs. In this example, the envelope
will be used to "play" a note by controlling the output
amplitude of an oscillator.
The p5.Oscillator sends its output through
an internal Web Audio GainNode (p5.Oscillator.output).
By default, that node has a constant value of 0.5. It can
be reset with the osc.amp() method. Or, in this example, an
Envelope takes control of that node, turning the amplitude
up and down like a volume knob.
To run this example locally, you will need the p5.sound library and a sound file.
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let osc, envelope, fft;
let scaleArray = [60, 62, 64, 65, 67, 69, 71, 72];
let note = 0;
function setup() {
createCanvas(710, 200);
osc = new p5.SinOsc();
// Instantiate the envelope
envelope = new p5.Env();
// set attackTime, decayTime, sustainRatio, releaseTime
envelope.setADSR(0.001, 0.5, 0.1, 0.5);
// set attackLevel, releaseLevel
envelope.setRange(1, 0);
osc.start();
fft = new p5.FFT();
noStroke();
}
function draw() {
background(20);
if (frameCount % 60 === 0 || frameCount === 1) {
let midiValue = scaleArray[note];
let freqValue = midiToFreq(midiValue);
osc.freq(freqValue);
envelope.play(osc, 0, 0.1);
note = (note + 1) % scaleArray.length;
}
// plot FFT.analyze() frequency analysis on the canvas
let spectrum = fft.analyze();
for (let i = 0; i < spectrum.length / 20; i++) {
fill(spectrum[i], spectrum[i] / 10, 0);
let x = map(i, 0, spectrum.length / 20, 0, width);
let h = map(spectrum[i], 0, 255, 0, height);
rect(x, height, spectrum.length / 20, -h);
}
}
