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 creating web-based audio applications. On the high-level, Tone offers common DAW (digital audio workstation) features like a global transport for synchronizing and scheduling events as well as prebuilt synths and effects. Additionally, Tone provides high-performance building blocks to create your own synthesizers, effects, and complex control signals.
Tone.js is also hosted at unpkg.com. It can be added directly within an HTML document, as long as it precedes any project scripts. [See the example here](https://github.com/Tonejs/Tone.js/blob/master/examples/simpleHtml.html) for more details.
The second argument is the duration that the note is held. This value can either be in seconds, or as a [tempo-relative value](https://github.com/Tonejs/Tone.js/wiki/Time).
The third (optional) argument of `triggerAttackRelease` is _when_ along the AudioContext time the note should play. It can be used to schedule events in the future.
Web Audio has advanced, sample accurate scheduling capabilities. The AudioContext time is what the Web Audio API uses to schedule events, starts at 0 when the page loads and counts up in **seconds**.
Tone.js abstracts away the AudioContext time. Instead of defining all values in seconds, any method which takes time as an argument can accept a number or a string. For example `"4n"` is a quarter-note, `"8t"` is an eighth-note triplet, and `"1m"` is one measure.
**IMPORTANT**: Browsers will not play _any_ audio until a user clicks something (like a play button). Run your Tone.js code only after calling `Tone.start()` from a event listener which is triggered by a user action such as "click" or "keydown".
`Tone.start()` returns a promise, the audio will be ready only after that promise is resolved. Scheduling or playing audio before the AudioContext is running will result in silence or incorrect scheduling.
`Tone.getTransport()` returns the main timekeeper. Unlike the AudioContext clock, it can be started, stopped, looped and adjusted on the fly. You can think of it like the arrangement view in a Digital Audio Workstation.
Multiple events and parts can be arranged and synchronized along the Transport. `Tone.Loop` is a simple way to create a looped callback that can be scheduled to start and stop.
Since Javascript callbacks are **not precisely timed**, the sample-accurate time of the event is passed into the callback function. **Use this time value to schedule the events**.
To create a **polyphonic** synthesizer, use `Tone.PolySynth`, which accepts a monophonic synth as its first parameter and automatically handles the note allocation so you can pass in multiple notes. The API is similar to the monophonic synths, except `triggerRelease` must be given a note or array of notes.
Sound generation is not limited to synthesized sounds. You can also load a sample and play that back in a number of ways. `Tone.Player` is one way to load and play back an audio file.
`Tone.loaded()` returns a promise which resolves when _all_ audio files are loaded. It's a helpful shorthand instead of waiting on each individual audio buffer's `onload` event to resolve.
Multiple samples can also be combined into an instrument. If you have audio files organized by note, `Tone.Sampler` will pitch shift the samples to fill in gaps between notes. So for example, if you only have every 3rd note on a piano sampled, you could turn that into a full piano sample.
In the above examples, the sources were always connected directly to the `Destination`, but the output of the synth could also be routed through one (or more) effects before going to the speakers.
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 and scheduling of parameters.
Tone.js creates an AudioContext when it loads and shims it for maximum browser compatibility using [standardized-audio-context](https://github.com/chrisguttandin/standardized-audio-context). The AudioContext can be accessed at `Tone.getContext`. Or set your own AudioContext using `Tone.setContext(audioContext)`.
Tone.js makes extensive use of the native Web Audio Nodes such as the GainNode and WaveShaperNode for all signal processing, which enables Tone.js to work well on both desktop and mobile browsers.
Tone.js runs an extensive test suite using [mocha](https://mochajs.org/) and [chai](http://chaijs.com/) with nearly 100% coverage. Passing builds on the 'dev' branch are published on npm as `tone@next`.
