rescript-tone

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