RHEOME / DOCUMENT RH-∞ / MUTAX
mutax
00Summary
A physical instrument for improvising live electronic music. Gestural control over rhythm, harmony, texture, and structure — all at once — so you can compose an emotional arc in real time.
When you play mutax you are the composer and the conductor at the same time: your movements guide the dynamics of a small MIDI orchestra you are scoring live. The name is mut- (change) plus -ax (a state of) — a system that is always in a state of change.
01Watch
02Why build one at all
Most electronic instruments are built to play back things you wrote earlier. They make it hard to change many tracks at once, and they sever the link between physical gesture and sound that every acoustic instrument takes for granted. Playing guitar, your body is the expression. On a laptop, you are designing music, not playing it.
Years of buying, touring with, and troubleshooting hardware setups led me to the same conclusion every other live-electronic improviser I found had reached: there is no off-the-shelf answer. Everyone builds their own bespoke rig. So mutax is mine — an interface rooted in tactile gesture that puts immediacy and spontaneity back into the performance.
03How it works
It runs on a Teensy 4.1 wired to a wall of key matrices and rotary encoders. The firmware is three engines running together:
- Looper. Everything you play is timestamped into a circular buffer. Hit a loop-length button and it grabs the last few bars and loops them — no arming, no red record light. (This is ammonite, grown into the whole.)
- Sequencer. A Euclidean sequencer per track, with a distribution parameter that pushes the pulses toward the front or back of the bar.
- Archetype engine. A menu of archetypal musical moves, split into harmonic (scale degrees and chord types against a global scale) and energetic (more energy, less energy, breakdown, four-on-the-floor).
Gesture ties them together. Hold the Wiichuck's Z button and the system drops into a transition state — the accelerometer performs fills, the joystick transposes octaves — and the moment you release, the cued harmonic and energetic changes apply to every track simultaneously.
04Build log
Bought a Digitakt and a Digitone. Beautiful machines, wrong job — they want you to arrange tracks ahead of time, not play them. This is where it starts: the itch for a box built for live creation instead of playback.
The Torso T-1 algorithmic sequencer opened my eyes to what live electronic improvisation could feel like. But the more I played it, the more I ran into a wall: I could not change the energy or emotion of the music fast enough, all at once, the way I heard it in my head.
Twenty minutes of improvisation a day on the T-1, writing down every single moment I wanted to change something and couldn't. Almost every note was about dynamics and the flow of energy — build-ups, drops, breakdowns. That notebook became the spec.
First stable platform working: a retroactive MIDI looper on a Teensy 4.1. Before I could build anything about musical change, I needed a rock-solid base to change. That looper is ammonite — the skeleton of this whole thing.
Scaled the hardware up: two more key matrices, three scanner ICs, eight more encoder boards, all hand-soldered across two perfboards. Integration ate the semester — I2C ghosting from splitting a matrix across two scanners, encoder boards reporting impossible addresses that would literally change overnight. After weeks of it I was basically back to where I'd been in December, with four weeks left before presentations.
Ported the Euclidean sequencer — the one I'd first built as a browser groovebox — from JavaScript into C++. Added a distribution parameter that weights the pulses toward the start or end of the bar. About a week and a half of porting.
The part that makes it mutax: a Wiichuck over I2C for gesture. Hold Z and the accelerometer performs fills while the joystick shifts octaves; let go and a whole cued-up harmonic and energetic change lands on every track at once. Composer and conductor at the same time.
Next: break the monolith into modular sub-modules that talk to the main Teensy over USB, and design a real PCB — a velocity keybed, an encoder bank, and a touch strip — building on the open Intech Grid schematics. Plus a parametric enclosure. Chris Kuscinsky (Critter & Guitari) said PCB first. He's right.
05Watch (Vimeo)
06Spec
| Type | hardware performance instrument (prototype) |
|---|---|
| Brain | Teensy 4.1 on a ProtoSupplies Project System baseboard |
| Controls | 3× 5×6 key matrices, 9 quad encoder boards, Wiichuck gesture |
| Firmware | C++ — retroactive looper + Euclidean sequencer + archetype engine |
| Clock | internal via uClock, or sync to external MIDI clock |
| Memory | timestamped MIDI in a circular PSRAM buffer |
| Name | mut- (change) + -ax (a state of) → always in a state of change |
07The lineage
mutax is the trunk. The other three grew into it or out of it:
- ammonite — the retroactive looper it was built on. The skeleton (filed under archive).
- drum-circles — where its Euclidean sequencer was first sketched, in the browser (filed under experiments).
- kymecreo — the velocity-sensitive key surface it wants for hands (filed under archive).
Shaped by Beardyman, Tim Exile, Onyx Ashanti, Imogen Heap and the Mi.Mu gloves, the Torso T-1, Author & Punisher.