JS-130

May 11, 2026 ยท View on GitHub

A synthesizer and sequencer that runs in your browser, using the WebAudio API.

Try it out here: https://www.joelstrait.com/jssynth/

Example Song

The song below is an example of what you can create with the JS-130, along with Beats Drum Machine and GarageBand.

JS-130 Example Song

Features

  • Oscillator Instruments
    • Base oscillator with sine/square/saw/triangle wave
    • Secondary oscillator with same wave types, and optional detune from primary oscillator
    • White or pink noise
    • Adjustable volume for each noise source (oscillator 1, oscillator 2, noise)
    • LFO to control oscillator pitch (i.e. "pitch wobble")
    • Filter, with LFO and ADSR envelope to control filter cutoff frequency
    • ADSR Envelope to control loudness
    • Feedback delay and reverb effects
  • Sampler Instruments
    • Use a sound file (*.wav, *.mp3, etc.) as an instrument
    • Filter, with LFO and ADSR envelope to control filter cutoff frequency
    • ADSR Envelope to control loudness
    • Feedback delay and reverb effects
  • Sequencer
    • Multiple tracks, each with its own instrument and set of patterns
    • Enter notes in patterns via on-screen piano keyboard, MIDI keyboard, or computer's keyboard
    • Full songs 1-99 patterns long
    • Volume control + mute for each track
  • Tempo control
  • Master volume control
  • On-screen keyboard to enter notes and try out sounds
  • MIDI keyboard support (only in browsers that support Web MIDI, such as Chrome)
  • Download sequencer output to a *.wav file

Running Locally

  • If running the app locally for the first time, run yarn install
  • Run yarn serve, which will build the app in-memory, and serve it using a local development server
  • Open one of the URLs listed in the command-line output in your browser
  • While the server is running the app will automatically be rebuilt each time the site is reloaded in the browser

Building For Production

  • If building the app for the first time, run yarn install
  • Run yarn build
  • The dist/ folder will contain the files that should be deployed to production

Running Tests

  • yarn test

Screenshots

Sequencer: JS-130 Sequencer

Instrument editor: JS-130 Instrument Editor

Pattern editor: JS-130 Pattern Editor