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These files are a format conversion of the MuScriptor weights released by Kyutai and Mirelo under CC BY-NC 4.0. They carry the same licence: non-commercial use only, attribution required. Requesting access confirms you accept those terms.
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MuScriptor for Core AI (.aimodel)
Apple Core AI conversions of MuScriptor, the open-weights audio-to-MIDI transcription model by Kyutai and Mirelo — the same weights, in the format macOS 27 runs on-device. Nothing was retrained, pruned or fine-tuned. These files exist so that a Mac can transcribe without Python or a GPU server.
| file | upstream | layers / width | size | note |
|---|---|---|---|---|
scribe-small-float32.aimodel |
MuScriptor/muscriptor-small | 14 / 768 | 398 MB | |
scribe-medium-float32.aimodel |
MuScriptor/muscriptor-medium | 24 / 1024 | 1.2 GB | the default |
scribe-large-float32.aimodel |
MuScriptor/muscriptor-large | 48 / 1536 | 5.1 GB | |
scribe-large-float16.aimodel |
same | 48 / 1536 | 2.6 GB | weights cast to half; twice as fast, exact on the reference clip |
Each .aimodel is a directory (main.mlirb, main.hash, metadata.json) with three entry points:
main (one decoder step with the attention cache as Core AI state), prefix (mel and instrument
conditioning) and embed. Everything around the model — the log-mel front end, resampling, the
token decoder, tie prologues, note cleanup, MIDI writing — lives in the Swift library.
Faithfulness
The conversion was held to upstream's Python code, not to a description of it:
- Token for token. On 7 clips × 3 sizes (19 runs, 25,000+ tokens, including a two-minute track), the Swift pipeline with these files reproduces upstream's greedy CPU fp32 decode exactly.
- Logits. Teacher-forced through the recorded token sequences, the decoder's logits agree with upstream's at ≥ 116 dB PSNR at every step, with no argmax flips.
- One thing had to be taken from the checkpoint rather than recomputed: the STFT window, which
the checkpoints store as a half-precision rounding of
torch.hann_window(2048). A float32 Hann window flips one near-tie token in 8 of 19 runs. The library carries the stored window. - Small fp16 is not shipped: it diverges after ~50 tokens, exactly where upstream's own fp16 run diverges. Large fp16 is exact on the reference clip and is included.
Measured against 712 sample-pack loops that ship their MIDI (medium, mir_eval, onset 50 ms and
pitch 50 cents, a per-file octave allowed because bass patches play below the written note): note
F1 0.53 with recall 0.69. The same MIDI rendered through a General MIDI piano and transcribed:
F1 0.95. Details and caveats in the library README.
Use
// swift-music-transcriber (MIT) — https://github.com/arraypress/swift-music-transcriber
let transcriber = try await MusicTranscriber(model: URL(fileURLWithPath: "scribe-medium-float32.aimodel"))
let result = try await transcriber.transcribe(audioURL)
try result.midi.write(to: outputURL)
hf download arraypress/scribe-muscriptor --include "scribe-medium-float32.aimodel/*" --local-dir models
scribe model install models/scribe-medium-float32.aimodel # the CLI built on the library
Requirements: macOS 27, Apple silicon. The model runs on the GPU (the ANE compiler pass rejects
these fp32 graphs); expectFrequentReshapes is set so the changing sequence length does not
respecialise per step.
Reproduce the conversion
The export is open source: Tools/export.py in the library repo, a uv script.
uv run Tools/export.py --size medium # coreai-torch 0.4.2, coreai-core 1.0.0b2, torch 2.13, Python 3.12
uv run Tools/export.py --size large --dtype float16
It downloads the gated upstream checkpoint with your own Hugging Face login, exports the decoder
with its KV cache as Core AI state, and writes the .aimodel. The Swift tests (ParityTests,
LogitParityTests) are the acceptance gate.
Licence and attribution
MuScriptor's weights are released under CC BY-NC 4.0 by Kyutai and Mirelo (github.com/muscriptor/muscriptor, code MIT). These files are a derivative of those weights and carry the same licence: non-commercial use only, with attribution to the original authors. The conversion tooling and the Swift library are MIT. If you use this, credit MuScriptor.
Model tree for arraypress/scribe-muscriptor
Base model
MuScriptor/muscriptor-large