VCV-Prototype/examples/vco.js

// Voltage-controlled oscillator example
// by Andrew Belt

// JavaScript isn't ideal for audio generating and processing due to it being 10-100 less efficient than C++, but it's still an easy way to learn simple DSP.

config.frameDivider = 1

var phase = 0
function process(args) {
	// Knob ranges from -5 to 5 octaves
	var pitch = args.knobs[0] * 10 - 5
	// Input follows 1V/oct standard
	pitch += args.inputs[0]

	// The relationship between 1V/oct pitch and frequency is `freq = 2^pitch`.
	// Default frequency is middle C (C4) in Hz.
	// https://vcvrack.com/manual/VoltageStandards.html#pitch-and-frequencies
	var freq = 261.6256 * Math.pow(2, pitch)
	display("Freq: " + freq.toFixed(3) + " Hz")

	// Accumulate phase
	phase += args.sampleTime * config.frameDivider * freq
	// Wrap phase around range [0, 1]
	phase %= 1

	// Convert phase to sine output
	args.outputs[0] = Math.sin(2 * Math.PI * phase) * 5
}