Play in a scale
Keys 0–6 select the seven degrees. A changes the root note, and B cycles through nine scales.
RP2040 · USB MIDI
ChoCo
An RP2040 USB MIDI controller for playing scale-aware chords.
Choose a scale degree with one of seven keys, move the joystick to change the chord, and send the result to a MIDI instrument or DAW. The OLED shows the active chord and modes.
THE CONTROLLER
What ChoCo does
ChoCo turns a small set of physical controls into scale-aware chords. The firmware runs on a Raspberry Pi Pico and sends standard MIDI notes over USB; a connected instrument makes the sound.
Change the chord
Move the joystick for suspensions, sevenths, extensions and other variations. Returning to center restores the base triad.
Choose how it plays
Latch, bass, strum, single-note and smart-voicing modes change how notes are played.
See the current state
The OLED shows the selected key and scale, chord name, active modes and harmonic suggestions.
USE & BUILD
Documentation and files
The handbook is a single page with a side index. It covers first use, controls, board connections, firmware, configuration and troubleshooting. The prototype’s printed back is shaped like a chocolate bar.
