imclab / synthjs

Extending the Web Audio API context with additional synth and DSP nodes

SynthJS v0.2.0-alpha

This is a utility script that extends the Web Audio API context with a number of common synth and DSP nodes. So far this consists of:

• White noise generator
• Envelope generator
• Feedback delay
• Reverb
• Drum sounds
• Looping sequencer

This is a work in progress.

Note: Requires a browser that supports the webkit Web Audio API (see: http://caniuse.com/audio-api).

Examples

A square wave "ping" with delay.

var context = new webkitAudioContext();

//square wave at 440 Hz (default)
var osc = context.createOscillator();
osc.type = osc.SQUARE;

//envelope with 0.001 sec attack and 0.5 sec decay
var envelope = context.createEnvelope(0.001, 0.5, 0, 0);

//feedback delay of 0.4 seconds with 0.5x feedback
var feedbackDelay = context.createFeedbackDelay(0.4, 0.5);

osc.connect(envelope);
envelope.connect(feedbackDelay);
envelope.connect(context.destination);
feedbackDelay.connect(context.destination);

//trigger the note and release after 0.6 seconds
envelope.trigger(0.6);

API

###Synths###

context.createNoiseGen([stereo [, bufferSize]]) - White noise generator

###Envelope###

context.createEnvelope(a, d, s, r)

Properties

• this.att
• this.dec
• this.sus
• this.rel

Methods

• trigger([length]) - Triggers a note. If length is supplied, the note will automatically be released after length seconds.
• release() - Releases the currently triggered note.

###Instruments###

context.createDrum() context.createHiHat()

Methods

• trigger

###Effects###

context.createFeedbackDelay(delay, feedback)

• delay is in seconds
• feedback is a value between 0 and 1.0

context.createReverbNode(length[, options])

• length is in seconds

Currently available keys for reverb options object:

• decay - how rapidly the sound decays (1 = linear decay, higher numbers are faster exponential decays) - defaults to 2
• reverse - pass in true for reverse reverb

###Looping###

Loop Class

Methods

• setInstruments
• setSequences
• setBPM
• setBeatUnit
• startLoop
• stopLoop

More detailed docs to come, for now check out example.html for an example of using the Loop class