Text prompts steer genre, mood, and tempo. Nothing in the prompt layer steers
harmony — no key, no chords, no changes. Below is that gap, measured against
Stable Audio 3, and what we found trying to close it through init_audio.
Press play.
Three generations from Stable Audio 3. The text prompt and seed never change — the only variable is a THIRI-computed harmonic skeleton conditioning the render. Switch sources mid-playback and hear the difference at the same bar.
Clip B lands on the chart — including the G♭dim7 chromatic passing chord THIRI's reharmonization engine inserted at bar 8 (it shares three of four tones with F7; voice-leading score 0.86).
Clip C moves the harmony without touching the prompt — bars 9–12 swap to the tritone-substitution branch (C7 → G♭7). The vibe stays; the changes move.
WHAT THIS SHOWS — AND WHAT IT DOESN'T. The gap is real and measured:
the text-only control grades 2 of 12 bars against the chart, which is chance.
Prompting does not hold harmony. But B and C landing on their charts is not
evidence the model read one. A pre-registered attribution sweep found accuracy tracks
how much of the THIRI skeleton survives diffusion (r = +0.98); at init_noise
0.9, where the skeleton is gone, accuracy falls back to 2 of 12. Both skeletons also
grade 12 of 12 alone — so leakage alone reaches the observed ceiling. Audio conditioning
is the wrong wire for symbolic control.
Read the full negative result →
Stable Audio 3 renders in seconds, on licensed data, with editing pros can trust — the hard infrastructure problems, already solved. The next question arrives with every working musician who picks it up: “can it follow my changes?” That's the question this page answers.
Genre, mood, instrumentation, tempo — the prompt layer is genuinely good at feel. A chart is a different kind of instruction, and that's the piece we bring: prompts keep the vibe, THIRI holds the changes.
The major-label alliances put professional creators on the roadmap — and pros arrive with changes in hand. THIRI is how the model follows them, demonstrated live above.
The pro surface taking shape around Stable Audio speaks the DAW's language — chord tracks, MIDI, sessions. THIRI is that vocabulary as a service, already running as an API.
You solved speed. You solved trust. Control is the race that's left — and harmonic control is the hardest half of it.
Where THIRI fitsTHIRI is a chord-intelligence engine: analysis, voicings, voice-leading, and reharmonization computed from pitch-class-set theory — not sampled from a language model. It answers the same way every time, in milliseconds, from a production API that agents and plugins can call directly.
Any musician-facing Stable Audio surface needs a chord lane the moment a player touches it. THIRI is that lane as a service — suggestion, voicing, reharmonization — without building a theory engine in-house.
Our own attribution test says the honest version out loud: harmony passed as audio can't be separated from the audio it rode in on. The fix isn't a better skeleton — it's a pathway that accepts chord symbols directly. THIRI supplies the labeled harmonic ground truth to train exactly that.
Inpainting rebuilds the sound; THIRI context tells each regenerated bar what it must resolve to — so every edit stays harmonically true to the surrounding track.
Agents composing with Stable Audio need harmony they can trust. THIRI's MCP server plans the arc; the model renders it.
Our team is registered for the Music Technology Hackathon Montreal, August 22–23 — building on Stable Audio 3. If you're at Stability and want the harmony rail under your model, talk to us before the demo does.
dennison@bluesprincemedia.com · engine live at chords.thiri.ai · MCP at mcp.thiri.ai