ReScript bindings for Tone.js, a Web Audio framework for creating interactive music in the browser.

Installation

npm install rescript-tone tone

Add to your rescript.json:

{
  "bs-dependencies": ["rescript-tone"]
}

Quick Start

// Create a synth and connect it to the speakers
let synth = Tone.Synth.make()
let node = synth->Tone.Synth.asAudioNode->Tone.AudioNode.toDestination
// Play a note
let _ = synth->Tone.Synth.triggerAttackRelease(440.0, Tone.Types.Time.seconds(0.5))
// Start the audio context (required by browsers)
let _ = Tone.Core.start()

Usage Examples

Playing Notes with a Synth

let synth = Tone.Synth.makeWithOptions({
  oscillator: ?Some({\"type": ?Some(Tone.Types.Sawtooth)}),
  envelope: ?Some({
    attack: ?Some(Tone.Types.Time.seconds(0.1)),
    decay: ?Some(Tone.Types.Time.seconds(0.2)),
    sustain: ?Some(0.5),
    release: ?Some(Tone.Types.Time.seconds(0.8)),
  }),
})
let _ = synth->Tone.Synth.asAudioNode->Tone.AudioNode.toDestination
let _ = synth->Tone.Synth.triggerAttackRelease(440.0, Tone.Types.Time.seconds(0.5))

Chaining Effects

let synth = Tone.Synth.make()
let reverb = Tone.Reverb.makeWithDecay(1.5)
let delay = Tone.FeedbackDelay.makeWithTimeFeedback(Tone.Types.Time.notation("8n"), 0.5)
let dest = Tone.Core.getDestination()
// Chain: synth -> delay -> reverb -> destination
let _ = synth
  ->Tone.Synth.asAudioNode
  ->Tone.AudioNode.chain([
    delay->Tone.FeedbackDelay.asAudioNode,
    reverb->Tone.Reverb.asAudioNode,
    dest->Tone.Destination.asAudioNode,
  ])

Scheduling with Transport

let synth = Tone.Synth.make()
let _ = synth->Tone.Synth.asAudioNode->Tone.AudioNode.toDestination
let transport = Tone.Core.getTransport()
// Set BPM
let bpm = transport->Tone.Transport.bpm
Tone.Param.setValue(bpm, 120.0)
// Schedule a repeating note
let _ = transport->Tone.Transport.scheduleRepeat(
  _time => {
    let _ = synth->Tone.Synth.triggerAttackRelease(440.0, Tone.Types.Time.notation("8n"))
  },
  Tone.Types.Time.notation("4n"),
)
// Start the transport
let _ = transport->Tone.Transport.start

Looping Patterns

let synth = Tone.Synth.make()
let _ = synth->Tone.Synth.asAudioNode->Tone.AudioNode.toDestination
let notes = ["C4", "E4", "G4", "B4"]
let seq = Tone.Sequence.makeWithSubdivision(
  (time, note) => {
    let _ = synth->Tone.Synth.triggerAttackReleaseAt(
      Tone.Types.Frequency.fromNotation(note),
      Tone.Types.Time.notation("8n"),
      ~time=Tone.Types.Time.fromFloat(time),
    )
  },
  notes,
  Tone.Types.Time.notation("4n"),
)
let _ = seq->Tone.Sequence.start
let _ = Tone.Core.getTransport()->Tone.Transport.start

Polyphonic Synth

let poly = Tone.PolySynth.makeWithOptions({maxPolyphony: ?Some(4)})
let _ = poly->Tone.PolySynth.asAudioNode->Tone.AudioNode.toDestination
// Play a chord
let _ = poly->Tone.PolySynth.triggerAttackRelease(
  [261.63, 329.63, 392.0],
  Tone.Types.Time.seconds(1.0),
)

API Reference

See docs/API.md for the complete API reference.

Architecture

The library is organized into modules that mirror Tone.js's structure:

Category	Modules
Core	`Core`, `Context`, `Transport`, `Destination`, `Param`, `AudioNode`, `Types`
Instruments	`Synth`, `AMSynth`, `FMSynth`, `MonoSynth`, `PolySynth`
Sources	`Oscillator`, `Player`, `Noise`
Effects	`Reverb`, `FeedbackDelay`, `Chorus`, `Distortion`, `AutoFilter`, `AutoPanner`, `AutoWah`, `BitCrusher`, `Chebyshev`, `Freeverb`, `JCReverb`, `Phaser`, `PingPongDelay`, `PitchShift`, `Tremolo`, `Vibrato`, `FrequencyShifter`, `StereoWidener`
Components	`Compressor`, `Limiter`, `Gate`, `Filter`, `EQ3`, `Panner`
Signal & Channel	`Signal`, `Volume`, `Gain`, `Channel`, `CrossFade`
Scheduling	`Loop`, `Event`, `Part`, `Sequence`

All modules are accessible under the Tone namespace (e.g., Tone.Synth.make(), Tone.Reverb.makeWithDecay(1.5)).

Each Tone.js class maps to a ReScript module with an abstract type t. Modules expose:

make / makeWithOptions constructors
@send methods for instance operations
@get / @set for properties
asAudioNode for casting to the base AudioNode.t type (for connect, chain, etc.)

Requirements

ReScript >= 12.0.0
Tone.js >= 15.0.0
A browser environment with Web Audio API support

License

MIT