Synth — live coded

Inspired by Sonic Pi, Overtone, and TidalCycles — live-coded music as a first-class way to explore sound.

A polyphonic subtractive synth whose patch parameters and control panel UI are both authored in Clojure. The DSP graph (oscillator → filter → gain → output) is a fixed Web Audio graph in the browser; an animation-frame loop polls the cljrs-side (patch) vector and pushes any changes onto the audio nodes. The control panel below is rendered by cljrs.ui — the editor source contains the entire hiccup tree, so the same code that draws the sliders also runs at build time to produce SEO-visible HTML.

Hold Alt (or Ctrl) and drag any number to scrub it live. Editing the source re-evals it; def'd atoms reset to source values, so source = preset / sliders = live tweak.

Keyboard: press Start first, then play with a s d f g h j k (white keys, C major) and w e t y u (black keys). Hold multiple keys for chords — up to 8 voices ring simultaneously. Each voice has its own ADSR.

What's happening

• The right-hand panel is rendered by cljrs.ui — the source defines a (ui-tree) hiccup vector and a (boot) entry point that calls (cljrs.ui/mount! "cljrs-root" ...).
• Each patch param is an atom declared with def at the top of the source. Slider :on-input handlers reset! the atom and re-mount; the editor's auto-apply re-binds them to the source values on every edit (so source = preset, sliders = live tweak).
• JS owns the AudioContext and the audio graph. An rAF loop calls repl.eval_floats("(patch)") every frame; if the vector changed it pushes new values onto the existing nodes with setValueAtTime.
• WAVE-TYPE is a keyword atom toggled by clicking the wave button; JS reads its name via repl.eval.
• Trigger re-runs the ADSR envelope. The wave-button + Trigger demonstrate two cljrs-driven controls (one inside the cljrs.ui tree, one outside in plain JS toolbar).
• Polyphony. Each held key gets its own Web Audio voice (osc → filter → gain) with an independent ADSR envelope. The voice table caps at 8 — past that, the oldest voice is stolen. Releasing a key triggers the release ramp; a delayed cleanup tears the voice down once it's silent. Live param edits propagate to every active voice so the chord morphs as you tweak.