014e636889
- section-energy: track activity matrix + volume/velocity multipliers per section - smart-chords: ChordEngine with voice leading, inversions, 4 emotion modes - hook-melody: melody engine with hook/stabs/smooth styles, call-and-response - mix-calibration: Calibrator module (LUFS volumes, HPF/LPF, stereo, sends, master) - transitions-fx: FX track with risers/impacts/sweeps at section boundaries - sidechain: MIDI CC11 bass ducking on kick hits via DrumLoopAnalyzer - presets-pack: role-aware plugin presets (Serum/Decapitator/Omnisphere per role) Full SDD pipeline (propose→spec→design→tasks→apply→verify) for all 7 changes. 302/302 tests passing.
87 lines
4.5 KiB
Markdown
87 lines
4.5 KiB
Markdown
# Proposal: Hook-Based Reggaeton Melody
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## Intent
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`build_lead_track()` generates random pentatonic notes — no hook, no identity, no rhythmic motif. Professional reggaeton leads have memorable hooks (repeating motif), rhythmic alignment with the dembow grid, call-and-response structure, and chord-tone emphasis on strong beats. This change replaces random generation with a structured hook engine producing identifiable, repeating motifs with controlled variation.
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## Scope
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### In Scope
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- **Hook engine module** (`src/composer/melody_engine.py`) — generates motifs, variations, call-response
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- **3 reggaeton styles**: "stabs" (syncopated hits on 1, 2.5, 3, 3.5), "smooth" (stepwise eighth notes), "hook" (arch contour, chord tones on strong beats)
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- **Motif + variation loop**: 2–4 bar motif repeated 2–4x with transpose/rhythmic-shift variations
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- **Call-and-response**: first half = call (ends on V/VII), second half = response (resolves to i)
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- **Chord-aware note selection**: strong beats (1, 3) favor chord tones; weak beats use scale passing tones
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- **Replace `build_lead_track()`** in `compose.py` to delegate to the new engine
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- **Tests** for deterministic output, motif identity preserved across variations, call-response resolution
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### Out of Scope
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- MIDI velocity humanization / groove quantization
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- User-selectable style at CLI (hardcoded to "hook" style initially)
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- Chord progression generation (uses existing `CHORD_PROGRESSION` from compose.py)
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- Pad/chords/bass refactoring — lead only
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## Capabilities
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### New Capabilities
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- `melody-engine`: Deterministic hook generation with motif, variation, call-response, and 3 reggaeton styles. Chord-aware via `CHORD_PROGRESSION` input.
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### Modified Capabilities
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- None at spec level. `build_lead_track()` API unchanged (same signature). Behavior changes from random to deterministic, but callers see same interface.
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## Approach
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New module `src/composer/melody_engine.py` with:
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1. **`build_motif(key_root, key_minor, style, bars=4)`** → `list[MidiNote]`
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- Style "hook": arch contour, chord tones on 0, 2, 4... beats, 4–8 notes
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- Style "stabs": short 16th hits on [1.0, 2.5, 3.0, 3.5] per bar
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- Style "smooth": stepwise scalar motion at eighth-note density
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- Chords resolved from `CHORD_PROGRESSION` for chord-tone selection
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2. **`apply_variation(motif, shift=0, transpose=0)`** → variation
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- Rhythmic shift: offset within the grid
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- Transpose: ±octave or ±third within scale
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3. **`build_call_response(motif, sections, key_root, key_minor)`** → `list[ClipDef]`
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- First half = call (motif + slight variation, ends on tension note)
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- Second half = response (motif, resolves to tonic)
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- Repeats for section length
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`compose.py` `build_lead_track()` becomes thin wrapper calling `melody_engine`. All existing tests pass with updated expected values.
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## Affected Areas
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| Area | Impact | Description |
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|------|--------|-------------|
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| `src/composer/melody_engine.py` | New | Hook engine — motifs, variations, call-response |
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| `scripts/compose.py` | Modified | `build_lead_track()` delegates to melody_engine; `get_pentatonic()` stays as helper |
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| `tests/test_compose_integration.py` | Modified | Update `test_melody_uses_pentatonic` to assert motif structure |
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| `tests/test_section_builder.py` | None | `get_pentatonic` tests unaffected |
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## Risks
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| Risk | Likelihood | Mitigation |
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|------|------------|------------|
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| Deterministic melody sounds repetitive | Med | 3 style options + variation params provide diversity; section energy scales velocity |
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| Chord-awareness breaks if CHORD_PROGRESSION changes format | Low | Hardcoded in compose.py — same module owns both; integration test catches mismatch |
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| Motif too short for long sections (8+ bars) | Low | Call-response repeats motif to fill bars; edge case validated in tests |
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## Rollback Plan
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Revert `build_lead_track()` to original random-pentatonic implementation (git revert). No schema or API changes — pure function replacement.
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## Dependencies
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- `CHORD_PROGRESSION` constant from `compose.py` (existing)
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- `get_pentatonic()` helper from `compose.py` (kept, reused)
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## Success Criteria
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- [ ] `build_lead_track()` produces identical output for same seed+key input (deterministic)
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- [ ] Generated melody contains a repeating 2–4 bar motif with ≤2 variations
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- [ ] Call section ends on V or VII degree; response resolves to i
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- [ ] Strong beats (quarter positions) use chord tones ≥70% of the time
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- [ ] All 110+ existing tests pass
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- [ ] 5+ new tests for melody_engine: motif identity, variation bounds, call-response resolution
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