Tone.js/Tone/instrument/PolySynth.js

define(["../core/Tone", "../instrument/Synth", "../source/Source"], function(Tone){

	"use strict";

	/**
	 *  @class  Tone.PolySynth handles voice creation and allocation for any
	 *          instruments passed in as the second paramter. PolySynth is
	 *          not a synthesizer by itself, it merely manages voices of
	 *          one of the other types of synths, allowing any of the
	 *          monophonic synthesizers to be polyphonic.
	 *
	 *  @constructor
	 *  @extends {Tone.Instrument}
	 *  @param {number|Object} [polyphony=4] The number of voices to create
	 *  @param {function} [voice=Tone.Synth] The constructor of the voices
	 *                                            uses Tone.Synth by default.
	 *  @example
	 * //a polysynth composed of 6 Voices of Synth
	 * var synth = new Tone.PolySynth(6, Tone.Synth).toMaster();
	 * //set the attributes using the set interface
	 * synth.set("detune", -1200);
	 * //play a chord
	 * synth.triggerAttackRelease(["C4", "E4", "A4"], "4n");
	 */
	Tone.PolySynth = function(){

		var options = Tone.defaults(arguments, ["polyphony", "voice"], Tone.PolySynth);
		Tone.Instrument.call(this, options);
		options = Tone.defaultArg(options, Tone.Instrument.defaults);

		//max polyphony
		options.polyphony = Math.min(Tone.PolySynth.MAX_POLYPHONY, options.polyphony);

		/**
		 *  the array of voices
		 *  @type {Array}
		 */
		this.voices = new Array(options.polyphony);
		this.assert(options.polyphony > 0, "polyphony must be greater than 0");

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

		//create the voices
		for (var i = 0; i < options.polyphony; i++){
			var v = new options.voice(arguments[2], arguments[3]);
			if (!(v instanceof Tone.Monophonic)){
				throw new Error("Synth constructor must be instance of Tone.Monophonic");
			}
			this.voices[i] = v;
			v.index = i;
			v.connect(this.output);
			if (v.hasOwnProperty("detune")){
				this.detune.connect(v.detune);
			}
		}
	};

	Tone.extend(Tone.PolySynth, Tone.Instrument);

	/**
	 *  the defaults
	 *  @const
	 *  @static
	 *  @type {Object}
	 */
	Tone.PolySynth.defaults = {
		"polyphony" : 4,
		"volume" : 0,
		"detune" : 0,
		"voice" : Tone.Synth
	};

	/**
	 *  Get the closest available voice, that is the
	 *  one that is either the closest to the note,
	 *  or has the lowest envelope value.
	 *  @param {Time} time return the voice that has the lowest energy at this time.
	 *  @param  {Note}  note  if there is a voice with this note, that should be returned
	 *  @return  {Tone.Monophonic}  A synth voice.
	 *  @private
	 */
	Tone.PolySynth.prototype._getClosestVoice = function(time, note){
		//play the note which has the same frequency, if that exists
		var sameNote = this.voices.find(function(voice){
			//break if it's within a small epsion of the voice's frequency
			if (Math.abs(voice.frequency.getValueAtTime(time) - Tone.Frequency(note)) < 1e-4 && 
				//and that note is currently active
				voice.getLevelAtTime(time) > 1e-5){
				return voice;
			} 
		});
		if (sameNote){
			return sameNote;
		}

		//find available notes
		var availableVoices = this.voices.filter(function(voice){
			//check that it's not ascending in energy (in attack phase)
			var levelNow = voice.getLevelAtTime(time);
			var nextLevel = voice.getLevelAtTime(time + this.sampleTime);
			//and it's near silent
			return levelNow >= nextLevel && voice.getLevelAtTime(time) < 1e-5;
		}.bind(this));

		if (availableVoices.length){
			//return the first one
			return availableVoices[0];
		}
		//otherwise take the one with the lowest energy
		var closestVoice = this.voices[0];
		this.voices.forEach(function(voice){
			if (voice.getLevelAtTime(time) < closestVoice.getLevelAtTime(time)){
				closestVoice = voice;
			}
		});
		return closestVoice;
	};

	/**
	 *  Trigger the attack portion of the note
	 *  @param  {Frequency|Array} notes The notes to play. Accepts a single
	 *                                  Frequency or an array of frequencies.
	 *  @param  {Time} [time=now]  The start time of the note.
	 *  @param {number} [velocity=1] The velocity of the note.
	 *  @returns {Tone.PolySynth} this
	 *  @example
	 * //trigger a chord immediately with a velocity of 0.2
	 * poly.triggerAttack(["Ab3", "C4", "F5"], undefined, 0.2);
	 */
	Tone.PolySynth.prototype.triggerAttack = function(notes, time, velocity){
		if (!Array.isArray(notes)){
			notes = [notes];
		}
		time = this.toSeconds(time);
		notes.forEach(function(note){
			var voice = this._getClosestVoice(time, note);
			voice.triggerAttack(note, time, velocity);
			this.log("triggerAttack", voice.index, note);
		}.bind(this));
		return this;
	};

	/**
	 *  Trigger the release of the note. Unlike monophonic instruments,
	 *  a note (or array of notes) needs to be passed in as the first argument.
	 *  @param  {Frequency|Array} notes The notes to play. Accepts a single
	 *                                  Frequency or an array of frequencies.
	 *  @param  {Time} [time=now]  When the release will be triggered.
	 *  @returns {Tone.PolySynth} this
	 *  @example
	 * poly.triggerRelease(["Ab3", "C4", "F5"], "+2n");
	 */
	Tone.PolySynth.prototype.triggerRelease = function(notes, time){
		if (!Array.isArray(notes)){
			notes = [notes];
		}
		time = this.toSeconds(time);
		notes.forEach(function(note){
			var voice = this._getClosestVoice(time, note);
			this.log("triggerRelease", voice.index, note);
			voice.triggerRelease(time);
		}.bind(this));
		return this;
	};

	/**
	 *  Trigger the attack and release after the specified duration
	 *
	 *  @param  {Frequency|Array} notes The notes to play. Accepts a single
	 *                                  Frequency or an array of frequencies.
	 *  @param  {Time} duration the duration of the note
	 *  @param  {Time} [time=now]     if no time is given, defaults to now
	 *  @param  {number} [velocity=1] the velocity of the attack (0-1)
	 *  @returns {Tone.PolySynth} this
	 *  @example
	 * //trigger a chord for a duration of a half note
	 * poly.triggerAttackRelease(["Eb3", "G4", "C5"], "2n");
	 *  @example
	 * //can pass in an array of durations as well
	 * poly.triggerAttackRelease(["Eb3", "G4", "C5"], ["2n", "4n", "4n"]);
	 */
	Tone.PolySynth.prototype.triggerAttackRelease = function(notes, duration, time, velocity){
		time = this.toSeconds(time);
		this.triggerAttack(notes, time, velocity);
		if (Tone.isArray(duration) && Tone.isArray(notes)){
			for (var i = 0; i < notes.length; i++){
				var d = duration[Math.min(i, duration.length - 1)];
				this.triggerRelease(notes[i], time + this.toSeconds(d));
			}
		} else {
			this.triggerRelease(notes, time + this.toSeconds(duration));
		}
		return this;
	};

	/**
	 * Sync the instrument to the Transport. All subsequent calls of
	 * [triggerAttack](#triggerattack) and [triggerRelease](#triggerrelease)
	 * will be scheduled along the transport.
	 * @example
	 * synth.sync()
	 * //schedule 3 notes when the transport first starts
	 * synth.triggerAttackRelease('8n', 0)
	 * synth.triggerAttackRelease('8n', '8n')
	 * synth.triggerAttackRelease('8n', '4n')
	 * //start the transport to hear the notes
	 * Transport.start()
	 * @returns {Tone.Instrument} this
	 */
	Tone.PolySynth.prototype.sync = function(){
		this._syncMethod("triggerAttack", 1);
		this._syncMethod("triggerRelease", 1);
		return this;
	};

	/**
	 *  Set a member/attribute of the voices.
	 *  @param {Object|string} params
	 *  @param {number=} value
	 *  @param {Time=} rampTime
	 *  @returns {Tone.PolySynth} this
	 *  @example
	 * poly.set({
	 * 	"filter" : {
	 * 		"type" : "highpass"
	 * 	},
	 * 	"envelope" : {
	 * 		"attack" : 0.25
	 * 	}
	 * });
	 */
	Tone.PolySynth.prototype.set = function(params, value, rampTime){
		for (var i = 0; i < this.voices.length; i++){
			this.voices[i].set(params, value, rampTime);
		}
		return this;
	};

	/**
	 *  Get the synth's attributes. Given no arguments get
	 *  will return all available object properties and their corresponding
	 *  values. Pass in a single attribute to retrieve or an array
	 *  of attributes. The attribute strings can also include a "."
	 *  to access deeper properties.
	 *  @param {Array=} params the parameters to get, otherwise will return
	 *  					   all available.
	 */
	Tone.PolySynth.prototype.get = function(params){
		return this.voices[0].get(params);
	};

	/**
	 *  Trigger the release portion of all the currently active voices.
	 *  @param {Time} [time=now] When the notes should be released.
	 *  @return {Tone.PolySynth} this
	 */
	Tone.PolySynth.prototype.releaseAll = function(time){
		time = this.toSeconds(time);
		this.voices.forEach(function(voice){
			voice.triggerRelease(time);
		});
		return this;
	};

	/**
	 *  Clean up.
	 *  @returns {Tone.PolySynth} this
	 */
	Tone.PolySynth.prototype.dispose = function(){
		Tone.Instrument.prototype.dispose.call(this);
		this.voices.forEach(function(voice){
			voice.dispose();
		});
		this._writable("detune");
		this.detune.dispose();
		this.detune = null;
		this.voices = null;
		return this;
	};

	/**
	 *  The maximum number of notes that can be allocated
	 *  to a polysynth.
	 *  @type  {Number}
	 *  @static
	 */
	Tone.PolySynth.MAX_POLYPHONY = 20;

	return Tone.PolySynth;
});