---
title: CODA
emoji: 🎵
colorFrom: indigo
colorTo: yellow
sdk: gradio
sdk_version: 6.16.0
python_version: '3.10'
app_file: app.py
pinned: false
license: mit
short_description: AI that finishes the song you quit on.
models:
  - stabilityai/stable-audio-3-small-music
---

# CODA — the songs you quit on, finished.

Everyone who's ever made music has one: the song that stops at 0:47. You ran out
of ideas at the bridge, the voice memo got buried, life happened. CODA takes that
unfinished clip and continues it into a longer, finished-sounding track — same
key, same tempo, same groove — then splices the new part onto your original so
cleanly you have to hunt for the seam.

One job, done well. No lyric bot, no cover-art printer — just a real, listenable
continuation of *your* clip, in 44.1 kHz stereo.

## How it works

1. **Listen.** librosa detects the key, tempo, and meter — pure DSP, no ML. If
   the recording is lo-fi (a voice memo, a phone capture, an old MP3 rip), CODA
   cleans a *copy* first — rumble filter, spectral noise gate, level — and
   conditions on that, so it follows the *song* and not the hiss. Your real
   original still goes into the final track (tick **remaster my part** to apply
   the same cleanup to your section too).
2. **Continue.** [Stable Audio 3 Small Music](https://huggingface.co/stabilityai/stable-audio-3-small-music)
   does the rest in a **single call**. SA3 is a latent-diffusion model with
   native audio *inpainting*: CODA places your clip at the front of the buffer
   and masks the region after it, and the model fills that region — conditioned
   on the whole clip — with a coherent continuation. No 30-second windows, no
   multi-pass chaining, no energy guards, no re-rolls. Eight diffusion steps with
   the pingpong sampler, a couple of seconds on a GPU. Leave the vibe box empty
   for a pure audio-led continuation that holds your key and tempo; type a vibe
   to creatively steer the new section.
3. **Stitch.** The continuation is loudness-matched to your recording, joined at
   the seam with a short equal-power crossfade, and faded out to a clean close.
   Everything is 44.1 kHz stereo — your original is resampled up to meet the SA3
   tail, never the other way around.

Progress streams through every stage, so you never stare at a dead screen.

## Why Stable Audio 3 (and not MusicGen)

CODA's earlier builds fought MusicGen's limits: a 30 s trained window forcing
fragile multi-pass chaining, 32 kHz mono output, and a tendency to drift into
silence on quiet prompts. SA3 Small Music removes all of it at once:

| | MusicGen-medium | SA3 Small Music |
|---|---|---|
| Continuation | chain 12 s-ctx / 18 s-new passes, compounding drift | one native inpaint call over the whole clip |
| Output | 32 kHz **mono** | **44.1 kHz stereo** |
| Speed | multiple passes per track | ~8 steps, a couple of seconds |
| License | CC-BY-NC (non-commercial) | Stability Community (commercial < $1M revenue) |

The hardest, most fragile part of the old build — the windowed chaining with its
energy guards and collapse re-rolls — is simply deleted.

## The stack — small on purpose

| Component | Size | Job |
|---|---|---|
| [Stable Audio 3 Small Music](https://huggingface.co/stabilityai/stable-audio-3-small-music) | ~0.6B | native audio-inpaint continuation |
| T5Gemma (bundled with SA3) | ~0.5B | optional text conditioning for the vibe box |
| librosa + SciPy | 0 params | key/tempo/meter detection, lo-fi cleanup |

Well under the 32B cap, runs entirely inside a single ZeroGPU window (generation
is seconds, not the whole budget), no cloud APIs.

## What it won't pretend to do

SA3 is a *music* model — the continuation is instrumental-leaning, and CODA
doesn't fake vocals it can't generate. The honest design choice: **your original
recording plays untouched up to the seam**, vocals and all, and the generated
section carries the music on from there. The band plays on; you write the next
verse. A typed vibe steers the new section creatively but can pull it away from
the original's exact key and tempo — that's the trade you're choosing when you
use it; leave it empty for a faithful continuation.

## Using it

Upload a WAV, MP3, or FLAC (a 15–30 second clip works best), or hit **try the
demo — PUSHBACK**. Set the finished length, optionally describe a vibe or tick
*remaster my part*, and press **Finish this song**. You'll see the detected
key/tempo the moment a clip loads, watch the stages stream, and get a 44.1 kHz
stereo track to play or download.

Run it locally (needs Python 3.10 and a CUDA GPU; the SA3 weights are gated, so
accept the licence on the model page and `huggingface-cli login` first):

```bash
pip install -r requirements.txt
python app.py
```

Deploying as a Space: because the SA3 weights are gated, add an **`HF_TOKEN`**
secret (from an account that has accepted the licence) in the Space settings, or
the model download 401s at startup. The bundled demo clip lives outside git (see
`.gitignore`) — upload `examples/pushback_demo.mp3` to the Space directly.

## Notes for the curious

`verify.py` is a dev-only QA harness: it measures the finished track against the
original for silence-collapse, clipping, seam continuity, tempo/key continuity,
spectral rolloff, and stereo width, and writes a diagnostic plot. It is not in
the app's runtime path — it's how regressions get caught between ear-checks.

Code is MIT. SA3 weights are under the
[Stability AI Community License](https://stability.ai/license) (free for
commercial use under $1M annual revenue) and bundle a T5Gemma encoder under the
Gemma Terms of Use — worth knowing if you fork it.

**Demo clip credit:** `examples/pushback_demo.mp3` is a clip by the band
**PUSHBACK**, sourced from TikTok, included solely as a sample to demonstrate the
tool. It is not affiliated with this project and all rights to the music remain
with the band. It's a deliberately lo-fi rip — which is the point: low-quality
in, finished-sounding out. If you are PUSHBACK and want it removed, say the word.

---

Built by Tony Winslow — Black Box Analytics — for the Build Small Hackathon 2026.