Computer plays four bars. You play four bars back. Then the computer answers, and you go again. It's the way jazz musicians have been talking to each other for a hundred years, only there's no human on the other side and no one is keeping score.
KEY
TEMPO · 96 BPM
VOICE
READY
Press Play to start trading.
—of 4
What's happening under the hood
Each round is four bars at 4/4. The computer phrase is one of twelve hand-written 4-bar melodies in C major, transposed to your chosen key. Phrases use scale degrees 1/2/3/5/6 — major pentatonic — so anything you play on top in those degrees fits.
Your keyboard has five keys mapped to those same pentatonic degrees. Hit a key and a note plays + writes itself onto the piano roll under the playhead. There's no scoring — the page records the exchange so you can hear the shape of the conversation.
Voice palettes: vib is three detuned sines with a soft attack, rhodes is a sine + 2× harmonic with quick decay, flute is a triangle wave with a slow attack curve. All Web Audio, no samples.
Pair with /cast-jam for free-time play, /cast-clap for strict rhythm matching, /cast-loop if you want to record what you played and loop it.
