Tier 1 — high-impact, low-friction (do after demo ships)
A. Mel-Band Roformer for vocal stems Beats BS-Roformer on vocals/drums/other. SDR 11.93 on Multisong (vs htdemucs_ft ~9). Branch already has BS-Roformer scaffold —
swap to Mel-Band variant + UVR checkpoint. Same code path. Direct ~+2 dB win.
- Repo: ZFTurbo/Music-Source-Separation-Training (https://github.com/ZFTurbo/Music-Source-Separation-Training) — pretrained
checkpoints
- Paper: Mel-Band RoFormer (arXiv 2310.01809) (https://arxiv.org/abs/2310.01809)
B. All-In-One Music Structure Analyzer (Bytedance / mir-aidj)
Replaces Beat-This! + librosa MFCC segmentation in ONE model. Joint output: beats + downbeats + tempo + functional segments (intro / outro / break / bridge / inst / solo / verse / chorus) + per-stem embeddings.
- Director's Phase 1 "drop only on drop-section" rule becomes empirically grounded instead of vibes — chorus and solo labels
available directly.
- Already uses demucs stems as input — we have those.
- SOTA on Harmonix Set. MIT licensed.
- Repo: mir-aidj/all-in-one (https://github.com/mir-aidj/all-in-one)
C. Meta Audiobox Aesthetics as critic
Reference-free music quality scorer. 4 axes: Production Quality, Production Complexity, Content Enjoyment, Content Usefulness.
Beats CLAP score for quality (CLAP measures semantic alignment, not perceptual quality — explicit warning in paper).
- Replaces unreliable CriticV2 (val acc 0.77 + codec bias) at zero training cost.
- Pretrained, open weights.
- Wire into /generate next to probes — second-opinion signal.
- Paper: Meta Audiobox Aesthetics (arXiv 2502.05139) (https://arxiv.org/html/2502.05139v1)
Tier 2 — bigger swaps (post-demo)
D. DJtransGAN as learned transition engine
ICASSP 2022. Differentiable EQ + fader + GAN trained on real DJ mixes. 70.5% preferred over rule-based crossfade in user study.
Backprop-able mix — could integrate into improver loop.
- Repo: ChenPaulYu/DJtransGAN (https://github.com/ChenPaulYu/DJtransGAN)
- Replace ~30% of transitions.py rules with learned variant.
E. ACE-Step (Apache 2.0) for generative bridges
Solves the audiocraft+ROCm blocker that killed our S8 plan. ACE-Step has explicit ROCm fork. Suno-quality, runs locally on AMD.
- Repo: isdood/ACE-Step-ROCm (https://github.com/isdood/ACE-Step-ROCm)
- Generate 8-bar bridges between BPM/genre-incompatible clips.
- Stable Audio Open 1.5 also viable (CC-trained data, no copyright issues).
- Alt: InstructME (latent diffusion + chord-progression matrix
constraint, multi-round edits). Stronger harmonic preservation
than ACE-Step; ROCm support not validated. Re-evaluate if ACE-Step
drift turns out high in transition-bridge use.
Paper: arXiv 2308.14360
Tier 3 — research-grade, experimental
F. MuQ-Eval as DPO reward signal
Music-specific quality metric. Could replace probe-severity as preference signal for S7 DPO — higher fidelity than aggregate
severity.
- Paper: MuQ-Eval (https://arxiv.org/html/2603.22677v1)
G. AudioMOS DORA-MOS (Challenge 2025 winner)
Pretrained MOS predictor — Mean Opinion Score for synthetic audio. Adds another head to the critic stack.
- AudioMOS Challenge 2025 (https://arxiv.org/html/2509.01336v1)
Tier 1 follow-up — depends on B (All-In-One) landing
H. Candidate-scored transition picker
Once All-In-One emits labeled segments (verse / chorus / break / pre-drop),
swap Director's ad-hoc junction selection for a 3-candidate-per-clip
scored picker: {verse_end, chorus_end, breakdown_start, pre_drop} ranked
by multi-factor score (energy-curve match, vocal-presence, key compat,
BPM strain, transition-type fit). Empirically grounded handoff points
rather than vibes. Inspired by kckDeepak/AI-DJ-Mixing-System.
- Trigger: after H lands All-In-One in src/all_in_one_wrapper.py
- Wire-in: ~50 lines in src/planner.py (replace junction-pick branch)
- Cost: free at inference (segments already computed for the labels)
I. EDMFormer — genre-specific structure for EDM pool (lands: tier1-upgrades)
Transformer for EDM-only structural segmentation: drop, buildup,
breakdown labels that All-In-One (trained on Western pop) misses.
AiJockey clip pool is EDM-heavy — All-In-One verse/chorus labels
systematically wrong for techno/dubstep/dnb/hardstyle where structure
is spectral-density driven, not chord-driven.
- Wire: invoke conditionally when Director classifies pool as EDM
(existing genre tag from prefix); fall back to All-In-One for
pop/non-EDM.
- Pairs with H (candidate-scored picker) — picker scores against
drop/buildup labels instead of pop verse/chorus.
- Paper: EDMFormer (arXiv 2603.08759)
- **BLOCKED**: as of 2026-05, no public checkpoint or training code
found. Track upstream for release; if authors don't publish weights,
self-train on EDM-98 dataset (98 annotated tracks) becomes the path
— small dataset, finetune from MERT/MusicFM may suffice. Re-evaluate
Q3 2026.
J. COCOLA scorer — stem-compat gate for mashup/stem_swap (lands: tier1-upgrades, low priority)
Contrastive model estimating harmonic + rhythmic coherence between
two stems. Pre-flight gate for Director's mashup_transition +
stem_swap_transition picks — reject incompatible pairs before render
instead of catching dissonance post-render in critic_v2 / probes.
- Source: github.com/gladia-research-group/cocola (Apache, public
checkpoints trained on MUSDB18-HQ/MoisesDB/Slakh2100/CocoChorales)
- Paper: arXiv 2404.16969 (COCOLA: Coherence-Oriented Contrastive
Learning of Musical Audio Representations)
- Wire: src/cocola_score.py wrapper; in planner.py mashup-pick branch
score candidate stem pairs, reject below threshold, cascade to
crossfade.
- **Low priority**: mashup_transition + stem_swap aren't frequent
Director picks. Most transitions go crossfade/eq_swap/filter_fade
where COCOLA never fires. Land if/when stem-overlay transitions
become a more common pick (e.g. after H candidate-scored picker
surfaces more mashup opportunities from labeled vocal segments).
Considered + dropped from this pass:
- FAD critic vs dj_sets_mp3 corpus — 25-set reference corpus too small
for stable Gaussian fit (standard FAD uses 1000s); Audiobox
Aesthetics (Tier1-C) covers similar perceptual-quality role
reference-free. Revisit only if reference corpus 10x'd.
- MusRec timbre morphing — duplicative with E (ACE-Step) generative
role; rock→deep-house style use case not in current pool;
diffusion latency cost not justified at Tier-3 priority. Park.
Cross-cutting techniques NOT yet evaluated (worth follow-up)
- DTW alignment at beat boundaries — eliminates phase cancellation probes are flagging (sub-sample beat snap)
- Spectral hold / freeze on genre jumps — cheap rule-based "glue layer"
- Tonal Pitch Space (TPS) — replaces Camelot wheel for non-Western scales
- EnCodec / DAC latent-space mixing — interpolate in neural-codec latent space instead of raw audio
My recommendation: 3 high-leverage moves post-demo
1. All-In-One Structure Analyzer — single biggest architectural win. Director gets ground-truth section labels. ~50 lines wire-in
+ replace madmom/librosa fallback. Likely closes ~30% of severity gap by alone.
2. Mel-Band Roformer vocals — branch scaffold ready. Drop checkpoint, flip flag. Audible win on stem-swap + mashup transitions.
3. Meta Audiobox Aesthetics as second-opinion critic — wire alongside probes in /generate header. Free quality signal. Replaces
CriticV2's training timeline.
Skip DJtransGAN + ACE-Step until demo ships. Both are real but week-of-work, not hour-of-work.
What this changes about backlog
Three of my "post-demo backlog" items get better alternatives:
- ~~CriticV2 retrain~~ → Meta Audiobox Aesthetics (no training)
- ~~MusicGen S8 (audiocraft blocked)~~ → ACE-Step ROCm fork
- ~~Beat-This! + sections separately~~ → All-In-One does both
Net: backlog shrinks, and quality ceiling rises.
Sources
- BS-RoFormer (lucidrains) (https://github.com/lucidrains/BS-RoFormer)
- Music-Source-Separation-Training (ZFTurbo) (https://github.com/ZFTurbo/Music-Source-Separation-Training)
- Mel-Band RoFormer paper (https://arxiv.org/abs/2310.01809)
- Mel-RoFormer for Vocal Separation
(https://www.researchgate.net/publication/383911604_Mel-RoFormer_for_Vocal_Separation_and_Vocal_Melody_Transcription)
- All-In-One Music Structure Analyzer (mir-aidj) (https://github.com/mir-aidj/all-in-one)
- All-In-One paper (arXiv 2307.16425) (https://arxiv.org/abs/2307.16425)
- Stable Audio Open 1.0 (HuggingFace) (https://huggingface.co/stabilityai/stable-audio-open-1.0)
- ACE-Step ROCm fork (https://github.com/isdood/ACE-Step-ROCm)
- ACE-Step 2026 guide (Spheron) (https://www.spheron.network/blog/deploy-open-source-ai-music-generation-gpu-cloud-2026/)
- DJtransGAN (ChenPaulYu) (https://github.com/ChenPaulYu/DJtransGAN)
- DJtransGAN paper (arXiv 2110.06525) (https://arxiv.org/abs/2110.06525)
- DJ AI: Optimizing Playlist Alignment (ACM 2025) (https://dl.acm.org/doi/10.1145/3771594.3771640)
- Meta Audiobox Aesthetics paper (https://arxiv.org/html/2502.05139v1)
- Meta Audiobox Aesthetics framework (https://www.emergentmind.com/topics/meta-audiobox-aesthetics)
- MuQ-Eval (https://arxiv.org/html/2603.22677v1)
- AudioMOS Challenge 2025 (https://arxiv.org/html/2509.01336v1)
- Survey on Evaluation Metrics for Music Generation (https://arxiv.org/html/2509.00051v1)
================================================================
SESSION 2026-05-11 RESEARCH ADDITIONS — output-quality backlog
================================================================
3 parallel research agents fired:
(A) latest 2026 music gen + flow-matching beyond VampNet/SAO/ACE-Step
(B) RLHF beyond DPO (IPO/KTO/ORPO/SLiC/PRM/GRPO/RLAIF for small N)
(C) source separation + DJ-tooling SOTA 2025-2026
Already shipped this session (don't re-do):
- 13 quality modules (sidechain, freq-mask, crowd, MS-widen, stem-norm,
LUFS-arc, BPM-grid, glitch-repair, critique, genre-rules, deesser,
CLAP-rerank, MERT-rerank) + 10 wired into call-sites.
- VampNet wrapper + pregrid + register (145 bridges in /cache).
- MERT-95M reward-head trained, sidecars on 83 clips.
- Adaptive LUFS, multi-Director sampling, _score_plan heuristic.
- TPS router, spectral_hold catalog entry, beat-align DTW phase fix,
spec-xfade STFT-domain crossfade.
- Matchering 2.0 master path + DeepAFx-ST wrapper.
- Stable Audio Open wrapper (gated on HF license accept).
- MuQ-Eval critic wrapper (real ID zhudi2825/MuQ-Eval-A1).
- DPO LoRA script extended w/ KTO + IPO + DPO-P loss variants.
TIER 1 (drop-in upgrades, low friction, biggest near-term lift)
----------------------------------------------------------------
A. Mel-Band-RoFormer-v2 — swap weights only, same wrapper.
vocal SDR 11.93 → 12.4 (+0.5 dB). MIT.
Repo: ZFTurbo/Music-Source-Separation-Training.
B. HTDemucs-6s — flag-enable in demucs main repo. Adds guitar+piano
stems. Free. MIT.
C. PESTO F0 (SonyCSLParis/pesto, ISMIR'23) — 50× faster than CREPE,
equal accuracy (RPA 95%+). Replace CREPE. MIT.
D. KTO training on accumulated render logs (already coded — flip
--loss-type kto when JSONL grows past ~50 labeled renders).
Beats DPO on our small/noisy regime, no pair construction needed.
E. ACE-Step v1.5 (replaces v1) — strict superset, Apache, ROCm-blessed,
<4 GB VRAM, <2s/full-song on A100. Patch ace_step_wrapper.py to
point at ace-step/ACE-Step-1.5.
F. All-In-One v1.1 (mir-aidj, retrained 2025) — drop-in. MIT.
TIER 2 (new wrappers / scripts, ~half-day each)
----------------------------------------------------------------
G. DrumSep (inagoy/drumsep, MIT) — kick/snare/toms/hat/cymbals sub-stems.
Useful for drum_replace transition precision + sidechain trigger band.
H. ChordFormer (Hyon/ChordFormer, ISMIR'24, Apache) — chord WCSR 84%
with confidence logits. Complements Camelot key on hip-hop/jazz.
I. InspireMusic-1.5B-48kHz (FunAudioLLM, Apache) — Qwen2.5-based AR
transformer + super-res flow-matching head. AR = streamable, low-
latency. Bridge gen alternative to VampNet/ACE-Step.
J. DiffRhythm 2 (ASLP-lab, Apache) — first open-weights flow-matching
song model. Long-form. Drop-in upgrade from DiffRhythm v1.
K. SCNet-XL (amanteur/SCNet-XL, MIT) — 6-stem (voc/drum/bass/guitar/
piano/other), SDR 10.5/9.8. Alternative to Demucs/RoFormer ensemble.
L. SimDPS retrieval-guided diffusion inpainting (arXiv 2509.16342,
Sep 2025) — uses our clip pool as retrieval corpus. R&D novelty.
M. DAC latent slerp + refinement (descriptinc/descript-audio-codec, MIT)
— latent-space bridge. Pair with SimDPS for inpainting refinement.
TIER 3 (heavier / research-grade, week-of-work)
----------------------------------------------------------------
N. PRM step-level reward shaping for Director plans — per-plan-step
Audiobox sub-scores. Lightman 2023 + Math-Shepherd 2024. Dense reward
beats outcome-only DPO/KTO. Requires step-level audio segmentation.
O. GRPO + RLAIF with Audiobox as online reward (MusicRL pattern,
Meta 2024 arXiv:2402.04229). Skip preference pairs; render-and-score
per rollout. Long-term endgame.
P. Constitutional self-rewarding (Bai 2022 + Self-Rewarding LM 2024) —
Director critiques own plans → synthetic preference pairs → expand
50 → 500 pairs before KTO/IPO. Data multiplier we already have via
director_critique.py — add pair-mining harness.
Q. TRIA (oreillyp.github.io/tria, ISMIR'25) — DAC masked-LM for drum
bridges specifically. Complements VampNet (which is general).
Track for weight release.
R. DJtransGAN port (ChenPaulYu, ICASSP'22) — 1-2d port. Replace rule-
based crossfade only IF render logs prove crossfade weakest tier
empirically.
S. DJMix-100 dataset (Yamaha + mir-aidj 2025, CC-BY-4.0) — 100 pro
mixes annotated with cue-points + transition types. Train a
transition classifier head; align to Director's tier vocabulary.
T. MERT/MusicFM cross-attention picker — replace CLAP-cosine clip-to-
prompt match with music-foundation features. MERT-v1-330M layer 6-8
mean pool. Music-aware vs text-music CLAP.
U. SongGeneration 2 / LeVo 2 (Tencent, Apache, 4B, beats Suno v5).
Heavyweight; monitor, evaluate when stack is more mature.
TIER 4 (operational / fixes / unblockers)
----------------------------------------------------------------
V. Fix vampnet_finetune.py dtype: coarse input is long (token ids) but
passed through Conv1d that expects float → cast inputs to long for
embedding lookup, NOT to conv path. Bug in our masked-LM loop.
W. Fix vampnet_dpo.py: weight_norm modules block deepcopy of reference
coarse. Solution: state-dict snapshot + on-the-fly clone, not
deepcopy(module).
X. Per-stem Audiobox prescore — current slice prescore is mix-only.
Adding per-stem (drums/bass/other) PQ predictions could improve
stem_swap picker.
Y. lufs_arc.py wire into master.py per-segment (currently unwired —
needs master() to accept segment energy hint).
Z. Library audio recovery alt source — YouTube yt-dlp bot-blocked.
Try: Spotify-via-Spotdl, Internet Archive mirror search, MusicBrainz
+ acoustid fingerprint. Or replace lost library entirely with
ACE-Step v1.5 generated CC-clean alternates.
AA. AESCA install for 3rd critic (CyberAgentAILab/aesca, AudioMOS
Challenge 2025 Track-2 winner). Apache. DORA-MOS not released.
SKIP PERMANENTLY (verified not viable)
----------------------------------------------------------------
- MelodyFlow (CC-BY-NC blocked)
- MusicGen audiocraft (CC-BY-NC blocked)
- Riffusion (quality too low)
- MusicLM (no public weights)
- LarsNet drums sub-stems (CC-BY-NC blocked)
- TempoCNN (AGPL)
- BandIt-v2 (cinematic stems, wrong domain)
- Open-Unmix streaming (SDR gap too big vs RoFormer)
- MAGNeT (CC-BY-NC blocked)
- EDMFormer (no public ckpt as of 2026Q2)
- SLiC-HF (superseded by IPO/DPO-P)
- ORPO (Qwen already instruction-tuned; marginal)
- Stable Audio Open (gated, needs manual HF license accept)
SOURCES added 2026-05-11
----------------------------------------------------------------
- ACE-Step 1.5 (https://github.com/ace-step/ACE-Step-1.5)
- DiffRhythm 2 (https://huggingface.co/ASLP-lab/DiffRhythm2)
- SongGeneration (https://huggingface.co/tencent/SongGeneration)
- InspireMusic-1.5B (https://huggingface.co/FunAudioLLM/InspireMusic-1.5B)
- TRIA (https://oreillyp.github.io/tria/) + arXiv 2509.15625
- VampNet (https://github.com/hugofloresgarcia/vampnet)
- KTO (Ethayarajh 2024, arXiv:2402.01306) — TRL KTOTrainer
- IPO (Azar 2023, arXiv:2310.12036) — TRL DPOConfig loss_type=ipo
- DPO-P (Pal 2024, arXiv:2402.13228) — TRL loss_type=dpop
- GRPO (DeepSeek, arXiv:2501.12948) — TRL GRPOTrainer
- MR-FlowDPO (arXiv:2512.10264) — multi-reward DPO for music
- MusicRL (Meta, arXiv:2402.04229) — RLAIF for music gen
- LeVo (arXiv:2506.07520) — multi-preference song generation
- SimDPS (arXiv:2509.16342) — similarity-guided diffusion inpainting
- Mel-Band-RoFormer-v2 weights (ZFTurbo/Music-Source-Separation-Training)
- SCNet-XL (amanteur/SCNet-XL)
- PESTO F0 (SonyCSLParis/pesto)
- DrumSep (inagoy/drumsep)
- ChordFormer (Hyon/ChordFormer, ISMIR'24)
- DJMix-100 dataset (Yamaha + mir-aidj 2025)
- Matchering 2.0 (sergree/matchering)
- DeepAFx-ST (Adobe Research, arXiv:2207.08759)
- Stable Audio Open paper (arXiv:2407.14358)
- DAC paper (arXiv:2306.06546)
PRIORITY ORDER (next session)
----------------------------------------------------------------
Highest output-quality ROI:
1. Tier-1 A/B/C/F drop-ins (~half day total).
2. Tier-1 E (ACE-Step v1.5) replace ACE-Step v1 wrapper.
3. Tier-4 V+W fix VampNet finetune/DPO bugs.
4. KTO training run when render-log has >= 50 labeled rows.
5. Tier-2 G/H/I wrappers (DrumSep, ChordFormer, InspireMusic).
6. Tier-2 L (SimDPS) — R&D experiment.
7. Tier-3 N (PRM step-level) — biggest long-term lever.
8. Tier-3 O (GRPO + RLAIF) — endgame after PRM matures.
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