Research map / Vision-language and multimodal / Human and embodied modeling
Toward Multimodal Sheet Music Recognition and Understanding
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Legato 2 is a system-by-system autoregressive optical music recognition pipeline with YOLO system segmentation, a text-aware byte-fallback ABC tokenizer, and it shows that OMR transcriptions improve frontier VLMs on sheet music understanding.
Problem
Optical music recognition of full-page sheet music scales poorly to long documents and ignores sequential structure, and existing neural OMR cannot transcribe embedded text such as titles and annotations; frontier VLMs also struggle with sheet music understanding.
Approach
Segment pages into systems with YOLO, then autoregressively transcribe each system into a system-level ABC representation conditioned on preceding system outputs (left-truncated context), using a byte-fallback BPE tokenizer that retains embedded text; the resulting transcription is also supplied as context to frontier VLMs.
Key results
- Legato 2 reduces page-level OMR-NED on Camera OpenScore String Quartets to 31.6 vs 58.2 for Legato 1 and 75.4 for Audiveris.
- On text recognition (Camera OpenScore String Quartets), Legato 2 reaches total CER 24.8% vs 58.1% for Gemini and 73.8% for Audiveris.
- Adding Legato 2 transcription as context raises Gemini 3.1 Pro SSMR-Bench accuracy from 71.4 to 92.7 and GPT-5 MusiXQA-style gains from 51.8 to 71.7 on SSMR-Bench.
Surprising findings
- Naive BPE tokenizer trained on text-inclusive data performs far worse than Legato 1 (e.g., 92.1 vs 58.2 OMR-NED on Camera String Quartets).
- Scaling the decoder (deep or wide) or using Qwen-3-VL-2B encoder yields little benefit on real-world datasets, attributed to a distribution shift from synthetic training data.
Limitations
- Trained only on synthetic PDMX-Synth renderings; distribution gap to real-world sheet music limits scaling benefits.
- Lyrics are excluded from transcription; merge step can discard trailing systems on ill-formed output.
- Multi-page evaluation restricted to Legato 1 vs 2 comparison due to computational cost; gains rely on YOLO segmentation quality.
Experimental setup
Datasets: PDMX-Synth PDMX IMSLP OpenScore String Quartets OpenScore Lieder MusiXQA SSMR-Bench
Benchmarks: PDMX-Synth Test Set Rendered OpenScore String Quartets Camera OpenScore String Quartets Rendered OpenScore Lieder Camera OpenScore Lieder IMSLP Piano Scores MusiXQA OMR split SSMR-Bench
Metrics: OMR-NED CER Unordered-CER G-Acc accuracy
Baselines: Legato 1 Audiveris Gemini 3.1 Pro GPT-5 PaddleOCR
Builds on: Legato YOLOv8 Llama-3.2-11B-Vision PDMX-Synth SMT-ABC Notation
Closest papers by meaning
- Transcoda: End-to-End Zero-Shot Optical Music Recognition via Data-Centric Synthetic Training (NeurIPS 2026 · similarity 0.92)
- Aria-MIDI: A Dataset of Piano MIDI Files for Symbolic Music Modeling (ICLR 2025 · similarity 0.87)
- N-gram Unsupervised Compoundation and Feature Injection for Better Symbolic Music Understanding (AAAI 2024 · similarity 0.86)
- Rubato: Transcribing Piano Music with Timestamps (NeurIPS 2026 · similarity 0.86)
- Unifying Symbolic Music Arrangement: Track-Aware Reconstruction and Structured Tokenization (NeurIPS 2025 · similarity 0.85)
- MuPT: A Generative Symbolic Music Pretrained Transformer (ICLR 2025 · similarity 0.85)
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