simplesynth.html

<script type="text/javascript">
	function clone(obj) {
		// A clone of an object is an empty object with a prototype reference to the original.
		// As such, you can access the current properties of the original through the clone.
		// If you set a clone's property, it will override the orignal's property, and
		// not affect the orignal. You can use the delete operator on the clone's overridden 
		// property to return to the earlier lookup behavior.

		function Clone() { } // a private constructor, used only by this one clone.
		Clone.prototype = obj;
		var c = new Clone();
		c.constructor = Clone;
		return c;
	}
	var lerp = function(start, target, amt){
		return start + (target-start) * amt;
	};
	var synth = {
		start: 0,
		ampEnv: [[400, 1],[20, 0]],
		ampEnvStep: 0,
		ampEnvAmt: 0,
		lastAmp: 0,
		freq: 0,
		audioRequest: function(count){
			//sample = dx.algo14(count);
			sample = Math.sin( count * this.freq ); // tone
			if(this.ampEnvStep < this.ampEnv.length){
				if ((1+count-this.start)/audioRate*this.ampEnv[this.ampEnvStep][0] > 1) {
					this.lastAmp = this.ampEnvAmt;
					this.ampEnvStep++;
					this.start = count;
				}else{
					this.ampEnvAmt = lerp(this.lastAmp, this.ampEnv[this.ampEnvStep][1], (1+count-this.start)/audioRate*this.ampEnv[this.ampEnvStep][0]);
				}
			}
			sample *=  this.ampEnvAmt;// vol
			return sample;
		},
		trigger: function(count, pitch, volume){
			this.start = count;
			this.lastAmp = volume;
			this.ampEnvStep = 0;
			this.freq = 440.0*Math.pow(2.0, (pitch-60)/12);
			this.freq *= 2*Math.PI/audioRate;
			dx.rf = this.freq;
		}
	};
	var m = Math;
	var dx = {
		f: [1,0.5,0.5,0.5,0,0],
		g: function(c,f){
			return this.f[f]*this.rf*c;
		},
		rf: 0,
		algo14: function(c){
			return m.sin(m.sin(this.g(c, 1))*this.g(c, 0))+m.sin(m.sin((m.sin(this.g(c, 4)+m.sin(this.g(c, 5)*m.sin(this.g(c, 5)))))*this.g(c, 3))*this.g(c, 2));
		}
	}
	// Create an Audio interface
	var output = new Audio();
	var audioRate = 44100.0;
	// Set up a mono channel at 44.1Khz
	output.mozSetup( 1, audioRate );  
	// samples/second * 120/1 * 60/1
	var beatLength = 60*audioRate/(120.0*16);
	var beat = 0;
	var triggers1 = [
		[1, 36], [1, 36], [1, 36], [0],
		[1, 36], [0], [1, 36], [0],
		[1, 36], [0], [1, 36], [0],
		[1, 36], [0], [1, 36], [1, 36],
		[1, 36], [0], [1, 36], [0],
		[1, 36], [0], [1, 36], [0],
		[1, 36], [1, 36], [0], [1, 36],
		[1, 36], [1, 36], [1, 36], [1, 36]
	];
	var triggers2 = [
		[0], [1, 56], [0], [1, 56],
		[0], [1, 56], [0], [1, 56],
		[0], [1, 56], [0], [1, 56],
		[1, 56], [1, 53], [1, 51], [1, 50]
	];
	synth2 = clone(synth);
	synth2.ampEnv = [[2, 1],[500, 0]];
	// Create a sample buffer array
	//num triggers, trigger size 
	var samples;
	
	function writeLong(){
		samples = new Float32Array( Math.ceil(32 * 16 * beatLength) );
		for(var i=0, l=samples.length; i<l; i++){
			remainder = i%beatLength;
			if(remainder == 0){
				if (triggers1[beat%triggers1.length][0] == 1) {
					synth.trigger(i, triggers1[beat%triggers1.length][1], 0);				
				};
				if (triggers2[beat%triggers2.length][0] == 1) {
					synth2.trigger(i, triggers2[beat%triggers2.length][1], 0);				
				};
				beat++;
			}
			samples[i] = synth.audioRequest(i)+synth2.audioRequest(i)*0.45;
		}
		return samples;
	}
	function writeShort(){
		samples = new Float32Array( Math.ceil(beatLength*30) );
		synth.ampEnv = [[2, 1],[500, 0]];
		synth.trigger(0, 36, 0);
		for(var i=0, l=samples.length; i<l; i++){
			samples[i] = synth.audioRequest(i);
		}
		return samples;
	}
</script>
<button onclick="output.mozWriteAudio( writeLong() );">Play</button>
<button onclick="output.mozWriteAudio( writeShort() );">Play Short</button>