Tone.js/Tone/effect/Tremolo.js

import Tone from "../core/Tone";
import "../component/LFO";
import "../effect/StereoEffect";

/**
 *  @class Tone.Tremolo modulates the amplitude of an incoming signal using a Tone.LFO.
 *         The type, frequency, and depth of the LFO is controllable.
 *
 *  @extends {Tone.StereoEffect}
 *  @constructor
 *  @param {Frequency} [frequency] The rate of the effect.
 *  @param {NormalRange} [depth] The depth of the effect.
 *  @example
 * //create a tremolo and start it's LFO
 * var tremolo = new Tone.Tremolo(9, 0.75).toMaster().start();
 * //route an oscillator through the tremolo and start it
 * var oscillator = new Tone.Oscillator().connect(tremolo).start();
 */
Tone.Tremolo = function(){

	var options = Tone.defaults(arguments, ["frequency", "depth"], Tone.Tremolo);
	Tone.StereoEffect.call(this, options);

	/**
	 *  The tremelo LFO in the left channel
	 *  @type  {Tone.LFO}
	 *  @private
	 */
	this._lfoL = new Tone.LFO({
		"phase" : options.spread,
		"min" : 1,
		"max" : 0,
	});

	/**
	 *  The tremelo LFO in the left channel
	 *  @type  {Tone.LFO}
	 *  @private
	 */
	this._lfoR = new Tone.LFO({
		"phase" : options.spread,
		"min" : 1,
		"max" : 0,
	});

	/**
	 *  Where the gain is multiplied
	 *  @type  {Tone.Gain}
	 *  @private
	 */
	this._amplitudeL = new Tone.Gain();

	/**
	 *  Where the gain is multiplied
	 *  @type  {Tone.Gain}
	 *  @private
	 */
	this._amplitudeR = new Tone.Gain();

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

	/**
	 *  The depth of the effect. A depth of 0, has no effect
	 *  on the amplitude, and a depth of 1 makes the amplitude
	 *  modulate fully between 0 and 1.
	 *  @type  {NormalRange}
	 *  @signal
	 */
	this.depth = new Tone.Signal(options.depth, Tone.Type.NormalRange);

	this._readOnly(["frequency", "depth"]);
	this.effectSendL.chain(this._amplitudeL, this.effectReturnL);
	this.effectSendR.chain(this._amplitudeR, this.effectReturnR);
	this._lfoL.connect(this._amplitudeL.gain);
	this._lfoR.connect(this._amplitudeR.gain);
	this.frequency.fan(this._lfoL.frequency, this._lfoR.frequency);
	this.depth.fan(this._lfoR.amplitude, this._lfoL.amplitude);
	this.type = options.type;
	this.spread = options.spread;
};

Tone.extend(Tone.Tremolo, Tone.StereoEffect);

/**
 *  @static
 *  @const
 *  @type {Object}
 */
Tone.Tremolo.defaults = {
	"frequency" : 10,
	"type" : "sine",
	"depth" : 0.5,
	"spread" : 180,
};

/**
 * Start the tremolo.
 * @param {Time} [time=now] When the tremolo begins.
 * @returns {Tone.Tremolo} this
 */
Tone.Tremolo.prototype.start = function(time){
	this._lfoL.start(time);
	this._lfoR.start(time);
	return this;
};

/**
 * Stop the tremolo.
 * @param {Time} [time=now] When the tremolo stops.
 * @returns {Tone.Tremolo} this
 */
Tone.Tremolo.prototype.stop = function(time){
	this._lfoL.stop(time);
	this._lfoR.stop(time);
	return this;
};

/**
 * Sync the effect to the transport.
 * @param {Time} [delay=0] Delay time before starting the effect after the
 *                              Transport has started.
 * @returns {Tone.Tremolo} this
 */
Tone.Tremolo.prototype.sync = function(delay){
	this._lfoL.sync(delay);
	this._lfoR.sync(delay);
	Tone.Transport.syncSignal(this.frequency);
	return this;
};

/**
 * Unsync the filter from the transport
 * @returns {Tone.Tremolo} this
 */
Tone.Tremolo.prototype.unsync = function(){
	this._lfoL.unsync();
	this._lfoR.unsync();
	Tone.Transport.unsyncSignal(this.frequency);
	return this;
};

/**
 * The Tremolo's oscillator type.
 * @memberOf Tone.Tremolo#
 * @type {string}
 * @name type
 */
Object.defineProperty(Tone.Tremolo.prototype, "type", {
	get : function(){
		return this._lfoL.type;
	},
	set : function(type){
		this._lfoL.type = type;
		this._lfoR.type = type;
	}
});

/**
 * Amount of stereo spread. When set to 0, both LFO's will be panned centrally.
 * When set to 180, LFO's will be panned hard left and right respectively.
 * @memberOf Tone.Tremolo#
 * @type {Degrees}
 * @name spread
 */
Object.defineProperty(Tone.Tremolo.prototype, "spread", {
	get : function(){
		return this._lfoR.phase - this._lfoL.phase; //180
	},
	set : function(spread){
		this._lfoL.phase = 90 - (spread/2);
		this._lfoR.phase = (spread/2) + 90;
	}
});

/**
 *  clean up
 *  @returns {Tone.Tremolo} this
 */
Tone.Tremolo.prototype.dispose = function(){
	Tone.StereoEffect.prototype.dispose.call(this);
	this._writable(["frequency", "depth"]);
	this._lfoL.dispose();
	this._lfoL = null;
	this._lfoR.dispose();
	this._lfoR = null;
	this._amplitudeL.dispose();
	this._amplitudeL = null;
	this._amplitudeR.dispose();
	this._amplitudeR = null;
	this.frequency = null;
	this.depth = null;
	return this;
};

export default Tone.Tremolo;