2.2 KiB
2.2 KiB
Accuracy experiments — 2026-10-31
Branch exp/accuracy. Every experiment is judged on both the synthetic tiers
(median merged-guitar pitch F1, ±50 ms) and the real reference song
Last Night on Earth (lnoe, the only reference with a trustworthy alignment:
constant +0.03 s, precision 93%). Swimming/Holes alignments are still flagged and
are not used for decisions.
Baseline before these experiments: synthetic full-mode guitar F1 t1a 0.43 · t1b 0.51 · t1c 0.39 · t1d 0.60; lnoe guitar F1 0.390.
| # | Experiment | Synthetic (median guitar F1) | lnoe guitar F1 | Verdict |
|---|---|---|---|---|
| E1 | Transcribe guitar from Demucs guitar + piano + other (instead of guitar stem only) | t1a 0.87 · t1b 0.81 · t1c 0.73 · t1d 0.72 | 0.403 | Adopted (commit 0f14fbc). Big synthetic gain is mostly a SONiVOX-timbre artefact (Demucs routes the synth guitar to piano/other); real gain is small but positive. t1a now passes. |
| E2 | Basic Pitch thresholds grid (onset 0.3–0.6, frame 0.2–0.4, min note 58/100 ms) | best ≈ default (0.5/0.3/58) | best 0.411 vs 0.403 | Not adopted — defaults are at the optimum on both. |
| E3 | Error taxonomy | — | fp: 46% no reference note near, 16% octave, 21% 50–150 ms timing; fn: 47% different pitch at the onset (partial chords), 25% octave, 24% missed | Octave fixing upper bound only 0.40 → 0.46 (pitch-class F1) with no systematic direction. |
| E4 | Complete partial strummed chords to standard guitar voicings (open + E/A-shape barres; maj/min/5/7/m7/sus/maj7) | −0.03…+0.03 | +0.016 (min 3 notes) | Not adopted yet — small, single-song evidence. |
Learnings
- Synthetic gains do not transfer 1:1 to real recordings while the synthetic guitar is the SONiVOX GM patch; a more realistic guitar sound in the renderer would make the synthetic benchmark more predictive.
- On real audio the limits are Basic Pitch's partial-chord recall on strummed rhythm guitar and octave confusions, not thresholds.
- An undocumented MT3 ONNX export exists (HF
ModernMube/HTDemucs_onnx, ~300 MB); not pursued — input/token format would need reverse-engineering and MT3 is weak on real recordings.
Experiment scripts live in the git-ignored .scratch/exp/.