arpeggio.thiri.ai
Helix — the arpeggiator that knows what chord it's sitting on
Every arpeggiator on the market repeats a pattern. Helix threads a path — voice-leading across an infinite octave lattice, with THIRI's harmonic engine keeping every note legal while Helix decides which legal note is musical. And its whole control surface is four knobs: small enough for an AI agent to play.
Not a loop — a path
Helix's engine is pure and deterministic: chord events in, note events out, seeded randomness so every phrase is reproducible. Feed it a progression and it voice-leads from chord to chord the way a player would — nearest-rung motion when you want glass, deliberate leaps when you want drama. You hear the resolution, not the pattern.
Four macros are the whole instrument
No patch pages, no menu diving. Everything Helix can do routes through four musical decisions:
Smoothness
Voice-leading temperament — glassy nearest-note motion at one end, wide deliberate leaps at the other.
Density
Quarter notes to thirty-seconds. The intensity pedal — thin behind a soloist, doubled for the climb.
Motion
Eight patterns — up, down, pendulum, converge, diverge, walk, chord, as-played. The shape of the line.
Adventure
Randomness temperature and reharmonization probability — how much risk the line is taking right now.
Plus voices (1–4), swing, tempo, and a harmony mode (off / 3rd / triad / block).
An instrument an agent can actually play
An AI agent can't play a keyboard — it has no hands, and it thinks in seconds, not microseconds. An agent-playable instrument needs three things, and Helix was built with all of them:
Playable by parameters
The four macros are a vocabulary an agent can reason about: "soloist is building — density up, smoothness toward leaps, adventure 60."
Musical between decisions
While the agent listens and thinks, the deterministic engine keeps generating in the chord from the last settings. The agent's silence sounds like intention, not absence.
Harmony-locked by construction
THIRI's engine guarantees every note is legal in the chord. The agent supplies judgment — phrasing, intensity, risk — never note-picking.
That's the stack: reflexes in the audio engine, harmonic knowledge in THIRI, musical judgment in the agent — each deciding at the speed that kind of decision actually happens. The agent doesn't make sound. It changes THIRI's mind, and THIRI's mind is just parameters.
Hear it before you read another word
The live instrument runs in your browser — load a progression, turn the macros, watch the lattice.