Tone.js/Tone/instrument/AMSynth.js

import Tone from "../core/Tone";
import "../instrument/Synth";
import "../signal/Signal";
import "../signal/Multiply";
import "../instrument/Monophonic";
import "../signal/AudioToGain";
import "../core/Gain";

/**
 *  @class  AMSynth uses the output of one Tone.Synth to modulate the
 *          amplitude of another Tone.Synth. The harmonicity (the ratio between
 *          the two signals) affects the timbre of the output signal greatly.
 *          Read more about Amplitude Modulation Synthesis on
 *          [SoundOnSound](https://web.archive.org/web/20160404103653/http://www.soundonsound.com:80/sos/mar00/articles/synthsecrets.htm).
 *          <img src="https://docs.google.com/drawings/d/1TQu8Ed4iFr1YTLKpB3U1_hur-UwBrh5gdBXc8BxfGKw/pub?w=1009&h=457">
 *
 *  @constructor
 *  @extends {Tone.Monophonic}
 *  @param {Object} [options] the options available for the synth
 *                            see defaults below
 *  @example
 * var synth = new Tone.AMSynth().toMaster();
 * synth.triggerAttackRelease("C4", "4n");
 */
Tone.AMSynth = function(options){

	options = Tone.defaultArg(options, Tone.AMSynth.defaults);
	Tone.Monophonic.call(this, options);

	/**
	 *  The carrier voice.
	 *  @type {Tone.Synth}
	 *  @private
	 */
	this._carrier = new Tone.Synth();
	this._carrier.volume.value = -10;

	/**
	 *  The carrier's oscillator
	 *  @type {Tone.Oscillator}
	 */
	this.oscillator = this._carrier.oscillator.set(options.oscillator);

	/**
	 *  The carrier's envelope
	 *  @type {Tone.AmplitudeEnvelope}
	 */
	this.envelope = this._carrier.envelope.set(options.envelope);

	/**
	 *  The modulator voice.
	 *  @type {Tone.Synth}
	 *  @private
	 */
	this._modulator = new Tone.Synth();
	this._modulator.volume.value = -10;

	/**
	 *  The modulator's oscillator which is applied
	 *  to the amplitude of the oscillator
	 *  @type {Tone.Oscillator}
	 */
	this.modulation = this._modulator.oscillator.set(options.modulation);

	/**
	 *  The modulator's envelope
	 *  @type {Tone.AmplitudeEnvelope}
	 */
	this.modulationEnvelope = this._modulator.envelope.set(options.modulationEnvelope);

	/**
	 *  The frequency.
	 *  @type {Frequency}
	 *  @signal
	 */
	this.frequency = new Tone.Signal(440, Tone.Type.Frequency);

	/**
	 *  The detune in cents
	 *  @type {Cents}
	 *  @signal
	 */
	this.detune = new Tone.Signal(options.detune, Tone.Type.Cents);

	/**
	 *  Harmonicity is the ratio between the two voices. A harmonicity of
	 *  1 is no change. Harmonicity = 2 means a change of an octave.
	 *  @type {Positive}
	 *  @signal
	 *  @example
	 * //pitch voice1 an octave below voice0
	 * synth.harmonicity.value = 0.5;
	 */
	this.harmonicity = new Tone.Multiply(options.harmonicity);
	this.harmonicity.units = Tone.Type.Positive;

	/**
	 *  convert the -1,1 output to 0,1
	 *  @type {Tone.AudioToGain}
	 *  @private
	 */
	this._modulationScale = new Tone.AudioToGain();

	/**
	 *  the node where the modulation happens
	 *  @type {Tone.Gain}
	 *  @private
	 */
	this._modulationNode = new Tone.Gain();

	//control the two voices frequency
	this.frequency.connect(this._carrier.frequency);
	this.frequency.chain(this.harmonicity, this._modulator.frequency);
	this.detune.fan(this._carrier.detune, this._modulator.detune);
	this._modulator.chain(this._modulationScale, this._modulationNode.gain);
	this._carrier.chain(this._modulationNode, this.output);
	this._readOnly(["frequency", "harmonicity", "oscillator", "envelope", "modulation", "modulationEnvelope", "detune"]);
};

Tone.extend(Tone.AMSynth, Tone.Monophonic);

/**
 *  @static
 *  @type {Object}
 */
Tone.AMSynth.defaults = {
	"harmonicity" : 3,
	"detune" : 0,
	"oscillator" : {
		"type" : "sine"
	},
	"envelope" : {
		"attack" : 0.01,
		"decay" : 0.01,
		"sustain" : 1,
		"release" : 0.5
	},
	"modulation" : {
		"type" : "square"
	},
	"modulationEnvelope" : {
		"attack" : 0.5,
		"decay" : 0.0,
		"sustain" : 1,
		"release" : 0.5
	}
};

/**
 *  trigger the attack portion of the note
 *
 *  @param  {Time} [time=now] the time the note will occur
 *  @param {NormalRange} [velocity=1] the velocity of the note
 *  @private
 *  @returns {Tone.AMSynth} this
 */
Tone.AMSynth.prototype._triggerEnvelopeAttack = function(time, velocity){
	//the port glide
	time = this.toSeconds(time);
	//the envelopes
	this._carrier._triggerEnvelopeAttack(time, velocity);
	this._modulator._triggerEnvelopeAttack(time);
	return this;
};

/**
 *  trigger the release portion of the note
 *
 *  @param  {Time} [time=now] the time the note will release
 *  @private
 *  @returns {Tone.AMSynth} this
 */
Tone.AMSynth.prototype._triggerEnvelopeRelease = function(time){
	this._carrier._triggerEnvelopeRelease(time);
	this._modulator._triggerEnvelopeRelease(time);
	return this;
};

/**
 *  clean up
 *  @returns {Tone.AMSynth} this
 */
Tone.AMSynth.prototype.dispose = function(){
	Tone.Monophonic.prototype.dispose.call(this);
	this._writable(["frequency", "harmonicity", "oscillator", "envelope", "modulation", "modulationEnvelope", "detune"]);
	this._carrier.dispose();
	this._carrier = null;
	this._modulator.dispose();
	this._modulator = null;
	this.frequency.dispose();
	this.frequency = null;
	this.detune.dispose();
	this.detune = null;
	this.harmonicity.dispose();
	this.harmonicity = null;
	this._modulationScale.dispose();
	this._modulationScale = null;
	this._modulationNode.dispose();
	this._modulationNode = null;
	this.oscillator = null;
	this.envelope = null;
	this.modulationEnvelope = null;
	this.modulation = null;
	return this;
};

export default Tone.AMSynth;