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renato97 014e636889 feat: professional reggaeton production engine — 7 SDD changes, 302 tests

- 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.

2026-05-03 23:54:29 -03:00

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Proposal: Hook-Based Reggaeton Melody

Intent

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.

Scope

In Scope

Hook engine module (src/composer/melody_engine.py) — generates motifs, variations, call-response
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)
Motif + variation loop: 2–4 bar motif repeated 2–4x with transpose/rhythmic-shift variations
Call-and-response: first half = call (ends on V/VII), second half = response (resolves to i)
Chord-aware note selection: strong beats (1, 3) favor chord tones; weak beats use scale passing tones
Replace build_lead_track() in compose.py to delegate to the new engine
Tests for deterministic output, motif identity preserved across variations, call-response resolution

Out of Scope

MIDI velocity humanization / groove quantization
User-selectable style at CLI (hardcoded to "hook" style initially)
Chord progression generation (uses existing CHORD_PROGRESSION from compose.py)
Pad/chords/bass refactoring — lead only

Capabilities

New Capabilities

melody-engine: Deterministic hook generation with motif, variation, call-response, and 3 reggaeton styles. Chord-aware via CHORD_PROGRESSION input.

Modified Capabilities

None at spec level. build_lead_track() API unchanged (same signature). Behavior changes from random to deterministic, but callers see same interface.

Approach

New module src/composer/melody_engine.py with:

build_motif(key_root, key_minor, style, bars=4) → list[MidiNote]
- Style "hook": arch contour, chord tones on 0, 2, 4... beats, 4–8 notes
- Style "stabs": short 16th hits on [1.0, 2.5, 3.0, 3.5] per bar
- Style "smooth": stepwise scalar motion at eighth-note density
- Chords resolved from CHORD_PROGRESSION for chord-tone selection
apply_variation(motif, shift=0, transpose=0) → variation
- Rhythmic shift: offset within the grid
- Transpose: ±octave or ±third within scale
build_call_response(motif, sections, key_root, key_minor) → list[ClipDef]
- First half = call (motif + slight variation, ends on tension note)
- Second half = response (motif, resolves to tonic)
- Repeats for section length

compose.py build_lead_track() becomes thin wrapper calling melody_engine. All existing tests pass with updated expected values.

Affected Areas

Area	Impact	Description
`src/composer/melody_engine.py`	New	Hook engine — motifs, variations, call-response
`scripts/compose.py`	Modified	`build_lead_track()` delegates to melody_engine; `get_pentatonic()` stays as helper
`tests/test_compose_integration.py`	Modified	Update `test_melody_uses_pentatonic` to assert motif structure
`tests/test_section_builder.py`	None	`get_pentatonic` tests unaffected

Risks

Risk	Likelihood	Mitigation
Deterministic melody sounds repetitive	Med	3 style options + variation params provide diversity; section energy scales velocity
Chord-awareness breaks if CHORD_PROGRESSION changes format	Low	Hardcoded in compose.py — same module owns both; integration test catches mismatch
Motif too short for long sections (8+ bars)	Low	Call-response repeats motif to fill bars; edge case validated in tests

Rollback Plan

Revert build_lead_track() to original random-pentatonic implementation (git revert). No schema or API changes — pure function replacement.

Dependencies

CHORD_PROGRESSION constant from compose.py (existing)
get_pentatonic() helper from compose.py (kept, reused)

Success Criteria

build_lead_track() produces identical output for same seed+key input (deterministic)
Generated melody contains a repeating 2–4 bar motif with ≤2 variations
Call section ends on V or VII degree; response resolves to i
Strong beats (quarter positions) use chord tones ≥70% of the time
All 110+ existing tests pass
5+ new tests for melody_engine: motif identity, variation bounds, call-response resolution

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