Music Information Retrieval (MIR) Tasks

Music Information Retrieval (MIR) tasks encompass the computational analysis, organization, and retrieval of music-related information from large audio databases. MIR is an interdisciplinary field that integrates musicology, signal processing, machine learning, information science, and cognitive research. Its overarching goal is to enable scalable music understanding, search, recommendation, and analytic applications, supporting both academic research and industrial systems such as streaming platforms and digital music libraries.

1. Core Definitions and Scope of MIR Tasks

Music Information Retrieval tasks are computational problems centered on extracting structured, semantically meaningful information from music signals and associated metadata. These tasks can be broadly classified into:

• Classification Tasks: Assigning categorical or multi-label descriptors to music items, including genre classification, instrument recognition, mood identification, artist recognition, and key detection.
• Regression and Sequence Estimation: Predicting continuous values or time-varying properties, such as emotion (arousal/valence), onset/beat positions, and melody or chord sequences.
• Annotation and Tagging: Multi-label tagging with genre, mood, instrument, or contextual labels, often based on large, weakly-supervised datasets.
• Entity Recognition and Linking: Identifying musical entities (works, contributors, performances) in text or user-generated content, and linking them to structured knowledge bases.
• Similarity and Retrieval: Computing distances or similarities between music items for search, recommendation, and clustering.
• Transcription and Structure Extraction: Deriving symbolic representations such as score, chord sequence, or lyrics from audio.
• Cross-modal and Cross-lingual Tasks: Bridging audio, symbolic (score), text, and video modalities, including multilingual access and retrieval.

MIR tasks can be conducted at various levels: excerpt/track-level (global), segment-level (per time window), or event/frame-level (temporal sequence).

2. Representative MIR Tasks and Benchmarking Practices

A comprehensive set of MIR tasks, as established in recent benchmarks such as MARBLE and CMI-Bench, includes:

Benchmarking protocols stress standardized splits and task-specific metrics, e.g., Accuracy and Macro F1 for classification; ROC-AUC/PR-AUC for tagging; $R^2$ for regression; WER/CER for transcription; and frame/tolerance-based measures for temporal sequence tasks.

3. Methodological Advances in MIR

Recent MIR research leverages a variety of modeling paradigms and representation learning methods:

• Feature Engineering: Traditional MIR relied on domain-informed features—MFCCs, chroma, spectral rolloff, tonnetz, and rhythm features—for classical machine learning classifiers (e.g., SVMs, kNN, Random Forests).
• Deep Architectures: The shift to deep learning introduced CNNs operating on spectrograms, CRNNs for sequential modeling, and Transformers for long-range dependencies.
• Transfer Learning: Convnet-based and transformer-based features pretrained on large music tagging corpora (e.g., Million Song Dataset, AudioSet) are now standard for transfer to downstream MIR tasks (Choi et al., 2017 ). Feature concatenation across intermediate CNN layers allows for task-adaptive transfer.
• Self-Supervised and Semi-Supervised Learning: Contrastive learning, as in CLMR and related methods, employs InfoNCE loss to learn augmentation-invariant or context-predictive representations from unlabeled music (Choi et al., 2022 ). Semi-supervised teacher-student training (“noisy student”) leverages large unlabeled corpora and iterative pseudo-labeling to scale model and data size, producing state-of-the-art results on MIR tasks (Hung et al., 2023 ).
• Codified Audio LLMing: CALM frameworks, such as Jukebox, directly model discretized audio token sequences using LLMs. Representations extracted from these models achieve superior results on tagging, genre, key, and emotion MIR tasks, notably filling “blind spots” in conventional tag-supervised feature sets (Castellon et al., 2021 ).
• Multi-Modal and Cross-Lingual Retrieval: Unified frameworks, such as CLaMP 3, align sheet music, MIDI, audio, and multilingual text in a joint embedding space, enabling cross-modal and cross-lingual retrieval in MIR and demonstrating emergent transfer even between previously unaligned modalities (Wu et al., 14 Feb 2025 ).
• Symbolic Representations: For tasks on score/MIDI data, matrix (pianoroll), sequence (tokenized), and graph neural representations are explored, each with unique tradeoffs for learning compositional or performance attributes (Zhang et al., 2023 ).

4. Evaluation Frameworks and Benchmark Datasets

Empirical evaluation in MIR requires standardized datasets and protocols. Notable resources include:

• FMA (Free Music Archive): Large, open, genre-hierarchical, copyright-cleared dataset with extensive audio and metadata; supports single- and multi-label MIR (Defferrard et al., 2016 ).
• MARBLE: Community-driven, multi-task, multi-dataset benchmark with a four-level task taxonomy (acoustic, performance, score, high-level description), standardized evaluation metrics, and public leaderboard (Yuan et al., 2023 ).
• CMI-Bench: Instruction-following benchmark recasting MIR annotations as LLM tasks; facilitates direct comparison between audio-text LLMs and traditional MIR systems, using the same metrics and datasets (Ma et al., 14 Jun 2025 ).
• mir_ref: Python framework for standardized, locally reproducible evaluation of music representations. Supports robustness testing (noise, gain, MP3 compression), downstream probes, and detailed error analysis (Plachouras et al., 2023 ).
• CCMusic: Unified, open-access database for Chinese MIR with standardized structure, label unification, and a dedicated multi-task evaluation framework (Zhou et al., 24 Mar 2025 ).
• Symbolic Data Resources: Datasets focusing on notation/symbolic music, relevant for composer/performance classification, difficulty rating, and structure modeling (Zhang et al., 2023 ).

Standard evaluation protocols include stratified artist splits to prevent overfitting, explicit reporting of metrics such as ROC-AUC, PR-AUC, macro/micro-F1, $R^2$, and SNR-based robustness assessments.

5. Methodological and Practical Considerations

MIR task implementation is affected by the following considerations:

• Segment Selection and Summarization: Generic summarization algorithms (e.g., GRASSHOPPER, LexRank, LSA, MMR) adapted from text summarization are effective at selecting brief, information-rich music excerpts. Such summaries improve classification accuracy compared to arbitrary 30-second contiguous segments and enable legal sharing of datasets (Raposo et al., 2015 ).

  Summarization Method	Key Idea	Output Selection
  GRASSHOPPER	Graph, diversity ranking	Iterative absorption-based sentence (segment) ranking
  LexRank	PageRank-style centrality	Most central/connected sentences
  LSA	SVD topic modeling	Sentences with highest topic weights
  MMR	Relevance/diversity trade	Maximize similarity to centroid, minimize redundancy
  Support Sets	Central passage sets	Sentences most supported by others

• Evaluation of Extractability and Robustness: Frameworks such as mir_ref demonstrate that many deep representations are not linearly separable for certain fine-grained MIR tasks (e.g., pitch), and robustness to noisy/degraded audio varies widely across embedding models.

• Cross-Modal and Cross-Lingual Generalization: Aligning music modalities (audio, score, text) supports emergent retrieval capabilities, even when no direct paired data is available (symbolic ↔ audio retrieval via shared text anchor) (Wu et al., 14 Feb 2025 ).
• Instruction-Following and LLM Evaluation: CMI-Bench reveals that current audio-text LLMs perform substantially below supervised models, particularly on structured/sequence prediction (beat, melody, performance techniques), and display systematic biases toward Western genres/instruments (Ma et al., 14 Jun 2025 ).
• Dataset Access and Cultural Inclusivity: Initiatives such as CCMusic ensure that diverse musical traditions (e.g., Chinese instruments and playing techniques) are represented, supporting both global benchmarking and culture-aware MIR advances.

6. Open Challenges and Future Trajectories

Key open research avenues in MIR tasks include:

• Scaling Unlabeled Data and Model Capacity: Evidence indicates that both model and data scaling, under semi-supervised paradigms, continue to yield performance improvements across varied MIR tasks (Hung et al., 2023 ).
• Task-appropriate Representation Learning: The optimal strategy for self-supervised music audio representation is task-dependent: multi-level output aggregation aids low-level (timbral) tasks, while sequential contrastive methods benefit high-level (semantic/global) tasks (Choi et al., 2022 ).
• Perceptually-Aligned Representations: Mel spectrograms remain superior to deep VQ representations for genre classification when training data is limited, due to their explicit correspondence with human auditory perception (Kamuni et al., 1 Apr 2024 ). Future work must bridge the gap between generative model features and classification tasks.
• Robustness, Generalization, and Bias Mitigation: Systematically testing models against real-world audio degradations, and analyzing performance across cultures, languages, and genres, are essential for practical deployment.
• Integration of Symbolic and Audio Modalities: Graph-based symbolic representations show promise for structurally rich, efficient MIR systems; further research may explore hybrid architectures and cross-modal transfer (Zhang et al., 2023 ).
• From Benchmarking to Instruction Tuning: Instruction-following benchmarks recast MIR tasks as language instructions, enabling direct LLM training, but further work is required to match specialist models, especially for structured and time-aligned outputs (Ma et al., 14 Jun 2025 ).

7. Practical Impact and Community Infrastructure

The MIR field has rapidly evolved toward large-scale, reproducible, and inclusive experimentation. Publicly available datasets (e.g., FMA, CCMusic), modular evaluation frameworks (MARBLE, mir_ref), and comprehensive benchmarks (CMI-Bench) collectively facilitate fair comparison, accelerate progress, and ensure diverse musical cultures are represented in both research and application settings. The emerging alignment of modality-universal and cross-lingual models signals a future where MIR systems can serve truly global, multimodal music understanding tasks.