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name: midi-preprocessing description: "Inspect and adapt deepjazz MIDI preprocessing, Metheny part assumptions, and grammar corpus extraction before LSTM generation." disable-model-invocation: true metadata: disco-role: operating license: Apache 2.0

deepjazz MIDI Preprocessing

Use this sub-skill when a task is about preparing or diagnosing MIDI input for deepjazz: checking whether a file matches the default Metheny assumptions, changing melody/accompaniment part selection, extracting chords and measures, or producing grammar corpus inputs for the LSTM route.

Do not rely on reading or running the original preprocessing script at runtime. This sub-skill distills the relevant behavior and provides a safe bundled inspection helper.

Route elsewhere

• For grammar token meanings, parse_melody, unparse_grammar, pruning, and note cleanup, use ../grammar-and-qa/.
• For Keras/Theano environment setup, LSTM training, generation constants, playback, and MIDI output writing, use ../lstm-generation/.
• For cross-cutting install/import failures that affect all routes, read ../../references/troubleshooting.md.

Start with a MIDI compatibility pass

1. Make sure music21 can parse the candidate MIDI file.

2. Run the bundled structure inspector before training or changing generator settings:

   python scripts/inspect_midi_structure.py --midi-file <input.mid> --melody-part 5 --accompaniment-parts 0,1,6,7 --start-offset 476 --end-offset 548
   

3. If the report warns that the melody part, accompaniment parts, or offset window do not contain the expected material, adapt the part indices/window before sending the file to the LSTM workflow.

4. Only after the file has plausible melody and chord material should you route to grammar extraction or generation.

What to read or run

• Read references/midi-preprocessing.md for the distilled get_musical_data(data_fn) and get_corpus_data(abstract_grammars) workflow, including the output objects expected by generation.
• Read references/data-assumptions.md before applying deepjazz to a new MIDI file; it lists the hard-coded Metheny arrangement assumptions and what to change.
• Read references/troubleshooting.md when music21 cannot parse a file, part indices fail, no chords appear, or measure/chord lengths do not match.
• Run scripts/inspect_midi_structure.py for a deterministic, no-training/no-playback report on MIDI parts, voices, offsets, chord-like events, and selected-window warnings.

Distilled API facts

Function	Inputs	Returns	Notes
get_musical_data(data_fn)	path to a MIDI file	(chords, abstract_grammars)	Internally parses the MIDI, selects hard-coded parts/window, groups measures, and converts melody measures into grammar strings.
get_corpus_data(abstract_grammars)	list of grammar strings	(corpus, values, val_indices, indices_val)	Flattens grammar tokens for LSTM sequence modeling and builds token-index maps.

Boundary checklist

• Owns: file parseability, part/window discovery, melody/chord extraction assumptions, corpus inputs.
• Does not own: exact grammar token semantics, note-generation choices, model architecture, training safety, or audio playback.
• Safe validation signal: a MIDI report with parse success, plausible selected melody/accompaniment material, and clear warnings for mismatches.