Tone.js is a Web Audio framework for creating interactive music in the browser. The architecture of Tone.js aims to be familiar to both musicians and audio programmers looking to create web-based audio applications. On the high-level, Tone offers common DAW (digital audio workstation) features like a global transport for scheduling and timing events and prebuilt synths and effects. For signal-processing programmers (coming from languages like Max/MSP), Tone provides a wealth of high performance, low latency building blocks and DSP modules to build your own synthesizers, effects, and complex control signals.
[SimpleSynth](http://tonejs.org/docs/#SimpleSynth) is a single oscillator, single envelope synthesizer. It's [ADSR envelope](https://en.wikipedia.org/wiki/Synthesizer#ADSR_envelope) has two phases: the attack and the release. These can be triggered by calling `triggerAttack` and `triggerRelease` separately, or combined as shown above. The first argument of `triggerAttackRelease` is the frequency, which can be given either a number (like `440`) or as "pitch-octave" notation (like `"D#2"`). The second argument is the duration of the envelope's sustain (i.e. how long the note is held for). The third (optional) argument of `triggerAttackRelease` is the time the attack should start. With no argument, the time will evaluate to "now" and play immediately. Passing in a time value let's you schedule the event in the future.
Any method which takes a time as a parameter will accept either a number or a string. Numbers will be taken literally as the time in seconds and strings can encode time expressions in terms of the current tempo. For example `"4n"` is a quarter-note, `"8t"` is an eighth-note triplet, and `"1m"` is one measure. Any value prefixed with `"+"` will be added to the current time. To trigger the same note one measure from now:
Time expressions are evaluated against the Transport's BPM. [Tone.Transport](http://tonejs.org/docs/#Transport) is the master timekeeper, allowing for application-wide synchronization of sources, signals and events along a shared timeline. Callbacks scheduled with Tone.Transport will be invoked right before the scheduled time with the exact time of the event is passed in as the first parameter to the callback.
//schedule a callback on the second beat of the first measure
Tone.Transport.schedule(function(time){
//schedule the synth's attackRelease using the passed-in time
synth.triggerAttackRelease("C4", "8n", time);
}, "1:2:0");
//start the transport
Tone.Transport.start();
```
[Read more about scheduling events with the Transport.](https://github.com/Tonejs/Tone.js/wiki/Transport)
### Loops
Instead of scheduling events directly on the Transport, Tone.js provides a few higher-level classes for working with events. [Tone.Loop](http://tonejs.org/docs/#Loop) is a simple way to create a looped callback that can be scheduled to start and stop.
Tone has a number of instruments which all inherit from the same [Instrument base class](http://tonejs.org/docs/#Instrument), giving them a common API for playing notes. [Tone.MonoSynth](http://tonejs.org/docs/#MonoSynth) is composed of one oscillator, one filter, and two envelopes connected to the amplitude and the filter frequency.
//pass in some initial values for the filter and filter envelope
var monoSynth = new Tone.MonoSynth({
"filter" : {
"type" : "lowpass",
"Q" : 7
},
"filterEnvelope" : {
"attack" : 0.02,
"decay" : 0.1,
"sustain" : 0.2,
"release" : 0.9,
}
}).toMaster();
//start the note "D3" one second from now
simpleSynth.triggerAttack("D3", "+1");
```
All instruments are monophonic (one voice) but can be made polyphonic when the constructor is passed in as the second argument to [Tone.PolySynth](http://tonejs.org/docs/#PolySynth).
```javascript
//a 4 voice MonoSynth
var polySynth = new Tone.PolySynth(4, Tone.MonoSynth).toMaster();
In the above examples, the synthesizer was always connected directly to the [master output](http://tonejs.org/docs/#Master), but the output of the synth could also be routed through one (or more) effects before going to the speakers.
```javascript
//create a distortion effect
var distortion = new Tone.Distortion(0.4).toMaster();
//connect a synth to the distortion
synth.connect(distortion);
```
[Read more about Effects](https://github.com/Tonejs/Tone.js/wiki/Effects)
# Sources
Tone has a few basic audio sources like [Tone.Oscillator](http://tonejs.org/docs/#Oscillator) which has sine, square, triangle, and sawtooth waveforms, a buffer player ([Tone.Player](http://tonejs.org/docs/#Player)), a noise generator ([Tone.Noise]((http://tonejs.org/docs/#Noise))), two additional oscillator types ([pwm](http://tonejs.org/docs/#PWMOscillator), [pulse](http://tonejs.org/docs/#PulseOscillator)) and [external audio input](http://tonejs.org/docs/#Microphone) (when [WebRTC is supported](http://caniuse.com/#feat=stream)).
```javascript
//a pwm oscillator which is connected to the speaker and started right away
var pwm = new Tone.PWMOscillator("Bb3").toMaster().start();
Like the underlying Web Audio API, Tone.js is built with audio-rate signal control over nearly everything. This is a powerful feature which allows for sample-accurate synchronization of multiple parameters with a single signal. Signals are built entirely without the ScriptProcessorNode so they do not introduce minimal processing overhead and no latency. Instead, this signal math and logic lets the native Web Audio GainNodes and WaveShaperNodes do all of the work meaning all processing is done in the underlying Assembly/C/C++ provided by the API. Signals are used extensively internally and are also useful for general DSP and control signal logic and transformations.
Tone.js creates an AudioContext when it loads and shims it for maximum browser compatibility. The AudioContext can be found at `Tone.context`. Or set your own AudioContext using `Tone.setContext(audioContext)`.
To use MIDI files, you'll first need to convert them into a JSON format which Tone.js can understand using [MidiConvert](http://tonejs.github.io/MidiConvert/).
Tone.js uses only one ScriptProcessorNode (in Tone.Meter). The rest of Tone's modules find a native Web Audio component workaround, making extensive use of the GainNode and WaveShaperNode especially, which enables Tone.js to work well on both desktop and mobile browsers. While the ScriptProcessorNode is extremely powerful, it introduces a lot of latency and the potential for glitches more than any other node.
# Contributing
There are many ways to contribute to Tone.js. Check out [this wiki](https://github.com/Tonejs/Tone.js/wiki/Contributing) if you're interested.
