chord_file_to_midi() parses the period in the user's original key (no
transposition), accumulates held-chord segments, then writes two pretty_midi
tracks: chords with root anchored at octave 4 (MIDI 60–71 + intervals) and
bass at octave 2 (MIDI 36–47). Extension notes are added as a fifth voice
at their standard interval above the root. Tempo is parameterised; the CLI
wrapper (python -m src.midi_export) supports --tempo BPM.
10 tests cover: file creation, parseability, instrument count and names,
chord/bass note counts for a 4-chord C-major fixture (14 chord + 4 bass),
octave placement assertions, and tempo affecting total duration.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
src/tokenizer.py:
- parse_chord_file(Path) → ChordPeriod: reads header + bar body, strips //
comments, validates bar position counts and chord symbols, raises
ChordFormatError with filename and bar number on any violation.
- transpose_to_canonical(ChordPeriod) → ChordPeriod: shifts all chord roots
and bass notes by the semitone offset to C major / A minor; fast-path
returns the original object when shift == 0.
tests/test_chord_file_parser.py: 39 tests covering parsing of 4 valid fixtures
(C major, F# major, B minor, G# minor), error messages for 2 invalid
fixtures, and transposition correctness including slash chord root+bass.
tests/fixtures/: 6 .chord fixture files (4 valid, 2 invalid).
requirements.txt: pinned to current latest stable versions
(torch 2.12.0, music21 10.1.0, pretty_midi 0.2.11, matplotlib 3.10.9,
numpy 2.4.6, pandas 3.0.3, pytest 9.0.3); Python >= 3.11 noted.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
H1K0