TabCNN — guitar tablature emission scorer (GGUF)

GGUF conversion of TabCNN for CrispASR's --tab surface. 833,982 parameters.

Per frame, the model emits six independent distributions over 21 fret classes — one per guitar string. It contains no decoder: no inter-string coupling, no temporal model, no search.

⚠️ These are emission SCORES, not a decided tablature. Turning them into a playable fingering needs a constrained decoder (one note per string, fret range, capo, hand span). Taking the argmax of this grid ignores every playability constraint. CrispASR ships the scorer and leaves the decoder to the caller.

Provenance and licence — verifiable, not asserted

Source artifact (fetch it and check the hashes yourself):

Every GGUF here carries these as metadata (general.source.url, general.source.record_url, general.source.md5_upstream, general.source.sha256), so provenance travels with the artifact.

⚠️ There is no Zenodo DOI for this record. 10.5281/zenodo.11406378 looks plausible and 404s — it does not exist. The record's actual DOI is the arXiv one, 10.48550/arXiv.2405.14679 (resolves). Cite what resolves.

Licence evidence. The Zenodo API reports, for record 11406378:

"metadata": { "license": {"id": "cc-by-4.0"}, "access_right": "open" }

Zenodo has no per-file licensing (a file object exposes only checksum, id, key, links, size), so the record licence governs every deposited file. And the record description states explicitly that the weights are part of the deposit:

"The weights for the best performing model (TabCNN trained with "GuitarProFX") in the paper are also provided."

That sentence is also what confirms this is the GuitarProFX-augmented variant rather than the baseline — the distinction that matters, since the baseline collapses from tablature F1 0.748 to 0.447 on real electric guitar while the augmented one recovers to 0.585 (DAFx-24).

Required citation (the record asks for this explicitly):

Pedroza HE, Abreu W, Corey R, Roman IR. "Leveraging real electric guitar tones and effects to improve robustness in guitar tablature transcription modeling." In 27th International Conference on Digital Audio Effects (DAFx), 2024.

Upstream chain:

Files

(F1 on EGSet12 track 01 against its JAMS ground truth; the +0.0017 is noise on a single 10 s clip — read it as "no loss", not "better".)

The output layer must stay at full precision

Only two tensors are quantizable at all: the conv stack is 3×3, so ne0=3, far below any block size, and the biases are 32–126 wide. dense0.weight (761 k of 834 k params) is effectively the whole model.

Quantizing dense0 costs nothing — but quantizing head.weight alongside it is catastrophic:

head.weight is 16 k params, 1.6 % of the file, and directly determines the 21-way per-string softmax. Preserving it makes Q4_0 as accurate as q8_0. crispasr-quantize encodes this as an arch rule; anyone converting these weights by another route should do the same.

⚠️ q4_k here is really Q4_0. No tensor has ne0 % 256 == 0 (dense0.weight is 5952; 5952 % 256 = 64), so k-quants cannot apply and the quantizer falls back to Q4_0. The filename keeps the requested name; the content is Q4_0.

Front end — read it from the file, do not assume it

CQT: sr 22050, hop 512, 192 bins, 24 per octave, fmin C1 (32.70 Hz)
  -> amplitude_to_db(ref = max of the WHOLE clip)   -> [-80, 0]
  -> /80 + 1                                        -> [0, 1]
  -> 9-frame centred context window

⚠️ fmin is C1, not the guitar's low E. Assuming E2 is the obvious guess and it is wrong — and every wrong value still runs, producing plausible tensors that pass shape and cosine checks while the model emits garbage. Measured on EGSet12 track 01: fmin C1 → tablature F1 0.771, E1 → 0.040, E2 at 44.1 kHz → 0.001. All of these constants are stored as GGUF metadata (tabcnn.sample_rate, tabcnn.fmin_hz, …) precisely so a consumer never has to guess.

⚠️ ref = max of the whole clip is a per-clip normalisation, so features cannot be computed streaming or chunked without changing them. This model is two-pass by construction.

Usage

crispasr --tab -m tabcnn-f16.gguf -f guitar.wav
crispasr --tab -m tabcnn-f16.gguf -f guitar.wav --tab-format json

For real use, take the log-probabilities through the C ABI (crispasr_session_tab → crispasr_session_tab_emissions) and run your own constrained decoder. crispasr_session_tab_silent_class() tells you which class means "not played" — read it rather than assuming it is the highest index.

Validation

crispasr-diff tabcnn against a reference dump from the amt-tools model, run from the waveform (not replayed features, so the CQT is covered):

End to end on EGSet12 track 01 against its JAMS ground truth:

ΔF1 +0.0024, argmax agreement 98.57 %. The residual difference is the front end — CrispASR uses direct Brown-kernel CQT against librosa's recursive downsampling — and it costs nothing on the task metric.

Limitations

• Trained on solo guitar. Mixed music is out of domain.
• GuitarSet numbers overstate real-world performance; EGSet12 is the honest reference point.
• The scorer is per-frame and per-string independent, so it can emit physically impossible combinations. That is expected — the decoder is where playability is enforced.