squelch

A playful little web tool for sketching acid basslines — inspired by the Sting device for Ableton, but built for the browser. Hit the smile, get a fresh 303-style line, and jam.

The focus is on the sequence generation and the squelchy acid feel — not a pixel-perfect 303 clone.

Play

• Space — start / stop playback
• G or the ☻ smile button — generate a new line (rerolls with the current settings)
• Tweak Sound (cutoff, resonance, env mod, decay, accent, drive, delay) and Generate (scale, key, steps, density, accents, slides, octaves) live — the loop updates on the next step, no stutter.

The current step lights up, accents glow amber, and slides show a magenta connector to the next note, so you can see what you're hearing.

Export to your DAW

Two buttons under the grid export the current line as a Standard MIDI File — the format both DAWs import natively. Accents become note velocity, slides become overlapping (legato) notes so a mono/portamento synth glides, and the tempo is embedded so it drops in at the right BPM (16 steps = one clean bar).

• Ableton Live — drag the .mid onto a MIDI track (or Create → Import MIDI File…). Point the track at a synth (Operator/Analog with mono + glide for the 303 feel). Live will offer to import the embedded tempo.
• FL Studio — File → Import → MIDI file (Ctrl+M), or drag the .mid into the Channel Rack / Playlist and pick a channel in the Import MIDI data dialog. The notes land in the Piano Roll; for slides, use a mono instrument with portamento.

Run

npm install
npm run dev      # open the printed localhost URL
npm run build    # static bundle in dist/, deployable anywhere

How it works

• Timing — a lookahead scheduler ("a tale of two clocks"): a coarse 25 ms setInterval schedules notes ~100 ms ahead on the sample-accurate AudioContext clock, so the groove never jitters.
• Voice — one persistent oscillator → resonant lowpass → amp. Each note fires a filter envelope (the squelch); accents hit harder and open the filter wider; slides glide the pitch and keep the gate open (legato).
• Generation — a biased random walk over a scale ladder with root-gravity, small melodic steps, occasional octave leaps, and sprinkled accents/slides — so lines feel intentional, not random.

Structure

src/
  audio/       AudioEngine (master chain) · AcidVoice (the 303 voice)
  sequencer/   Scheduler (transport) · generator · types
  music/       scales & MIDI helpers
  export/      Standard MIDI File writer (Ableton / FL Studio)
  ui/          DOM rendering, controls, playhead + scope
  main.ts      composition root