Heuristic 1
Calculation of Distinctive Note Velocity/Onset Deviation Ratios
Heuristic 2
Calculation of Note Onset Median Metric Level
Figure 1
Four classes (NE = non‑expressive, EO = expressive onset, EV = expressive velocity, and EP = expressively performed) using heuristics in Section 4.2 for the expressive performance detection of MIDI tracks in GigaMIDI.
Table 1
Sample of symbolic datasets in multiple formats, including MIDI, ABC, MusicXML, and Guitar Pro formats.
| Dataset | Format | Files | Hours | Instruments |
|---|---|---|---|---|
| GigaMIDI | MIDI | >1.43M | >40,000 | Misc. |
| MetaMIDI | MIDI | 436,631 | >20,000 | Misc. |
| Lakh MIDI | MIDI | 174,533 | >9,000 | Misc. |
| DadaGP | Guitar Pro | 22,677 | >1,200 | Misc. |
| ATEPP | MIDI | 11,677 | 1,000 | Piano |
| Essen Folksong | ABC | 9,034 | 56.62 | Piano |
| NES Music | MIDI | 5,278 | 46.1 | Misc. |
| MID‑FiLD | MIDI | 4,422 | >40 | Misc. |
| MAESTRO | MIDI | 1,282 | 201.21 | Piano |
| Groove MIDI | MIDI | 1,150 | 13.6 | Drums |
| JSB Chorales | MusicXML | 382 | >4 | Misc. |
[i] ATEPP = Automatically Transcribed Expressive Piano Performances.
Figure 2
Distribution of the duration in bars of the files from each subset of the GigaMIDI dataset. The x‑axis is clipped to 300 for better readability.
Table 2
Number of MIDI note events by instrument group in percentage (IGN = instrument group number, CP = chromatic percussion, and FX = effect).
| IGN: 1‑8 | Events | IGN: 9‑16 | Events |
|---|---|---|---|
| Piano | 60.2% | Reed/Pipe | 1.1% |
| CP | 2.4% | Drums | 17.4% |
| Organ | 1.8% | Synth Lead | 0.5% |
| Guitar | 6.7% | Synth Pad | 0.6% |
| Bass | 4.2% | Synth FX | 0.3% |
| String | 1.1% | Ethnic | 0.3% |
| Ensemble | 2.1% | Percussive FX | 0.3% |
| Brass | 0.7% | Sound FX | 0.3% |
Figure 3
Distribution of files in GigaMIDI according to (a) MIDI notes, and (b) ticks per quarter note (TPQN).
Figure 4
Musicmap style topology (Crauwels, 2016).
Figure 5
Distribution of musical style in GigaMIDI.
Figure 6
Example of each duple onset metric level grid in different colors using circles and dotted lines for the position of onsets, where k = 6.
Table 3
Optimal threshold selection results based on the 80% training set, showing the optimal threshold value for each heuristic where the P4 value is maximized.
| Heuristic | Threshold | P4 |
|---|---|---|
| Distinct velocity | 52 | 0.7727 |
| Distinct onset | 42 | 0.7225 |
| DNVR | 40.965% | 0.7727 |
| DNODR | 4.175% | 0.9529 |
| NOMML | Level 12 | 0.9952 |
Table 4
Detection results (%) for expressive performance in each MIDI track class within the GigaMIDI dataset.
| Class | & |
|---|---|
| NE (62.5%) | < 42 & < 52 |
| EO (7.2%) | ≥ 42 & < 52 |
| EV (27.4%) | < 42 & ≥ 52 |
| EP (2.9%) | ≥ 42 & ≥ 52 |
[i] The analysis is based on the number of distinct velocity levels (D‑V = distinct velocity) and onset‑time deviations (D‑O = distinct onset). Categories include non‑expressive (NE), expressive onset (EO), expressive velocity (EV), and expressively performed (EP).
Table 5
Results (%) of expressive performance detection for each MIDI track class in GigaMIDI based on the calculation of (DNODR), and (DNVR).
| Class | & |
|---|---|
| NE (52.3%) | < 4.175% & < 40.965% |
| EO (9.1%) | ≥ 4.175% & < 40.965% |
| EV (24.2%) | < 4.175% & ≥ 40.965% |
| EP (14.4%) | ≥ 4.175% & ≥ 40.965% |
Figure 7
Distribution of MIDI tracks according to (a) NOMML (level between 0 and 12, where k = 6) for MIDI tracks in GigaMIDI. The NOMML heuristic investigates duple and triplet onsets, including onsets that cannot be categorized as duple‑ or triplet‑based MIDI grids, and (b) instruments for expressively performed tracks in the GigaMIDI dataset.
Table 6
Classification accuracy of each heuristic for expressive performance detection.
| Detection heuristics | Classification accuracy | Ranking |
|---|---|---|
| Distinct velocity | 77.9% | 4 |
| Distinct onset | 77.9% | 4 |
| DNVR | 83.4% | 3 |
| DNODR | 98.2% | 2 |
| NOMML | 100% | 1 |
Table 7
True positives (TP), true negatives (TN), false positives (FP), and false negatives (FN) based on the threshold set by P4 for heuristics, including correct negatives (CN) (in percentages).
| Heuristic (%) | TP | TN | FP | FN | CN |
|---|---|---|---|---|---|
| Distinct velocity | 35.4 | 42.5 | 21.2 | 0.9 | 98.0 |
| Distinct onset | 24.8 | 53.1 | 10.6 | 11.5 | 82.2 |
| DNVR | 35.4 | 48.0 | 21.2 | 0.9 | 98.2 |
| DNODR | 34.5 | 63.7 | 0 | 1.77 | 97.3 |
| NOMML | 36.3 | 63.7 | 0 | 0 | 100 |