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.
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renato97
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.sdd/changes/sidechain/proposal.md
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.sdd/changes/sidechain/proposal.md
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# Proposal: 808 Bass Sidechain Ducking
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## Intent
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808 bass and kick drum overlap in low frequencies with zero separation. Professional reggaeton uses sidechain-style ducking — bass dips when kick hits — creating the "pumping" feel and preventing low-frequency mud. Currently `build_bass_track()` generates static-velocity MIDI notes with no awareness of the drumloop's kick pattern.
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## Scope
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### In Scope
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- Pre-analyze drumloop WAV files to extract kick transient positions via `DrumLoopAnalyzer`
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- Cache kick beat-positions per drumloop path (same file reused across sections)
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- Generate MIDI CC11 (Expression) events on bass clips at kick hit positions
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- Duck shape: instantaneous drop to CC11≈50, 80ms release ramp to CC11=127
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- `ClipDef` schema extended with `midi_cc: list[CCEvent]` field
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- `RPPBuilder._build_midi_source()` emits CC E-lines interleaved with Note events
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### Out of Scope
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- Track-level volume automation envelopes (`VOLENV2`) — complex binary encoding, deferred
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- ReaComp-sidechain routing via ReaScript — Phase 2 enhancement only
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- DrumLoopAnalyzer integration at composition time (not pre-cached) — deferred to Phase 2
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- Ducking for non-bass tracks (chords, lead, pad)
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- User-configurable duck depth/shape — constants only
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## Capabilities
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### New Capabilities
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- `midi-cc-events`: MIDI CC event emission in `.rpp` source — CC11 Expression events interleaved with notes in E-line stream
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- `kick-detection-cache`: `DrumLoopAnalyzer` tied into composition pipeline; kick positions cached per drumloop WAV path
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### Modified Capabilities
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- `bass-generation`: `build_bass_track()` accepts kick position data and generates per-note velocity ducking OR CC11 events synchronized to kick hits
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- `rpp-clip-encoding`: `_build_midi_source()` emits `E B0 0B xx` lines alongside Note On/Off
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## Approach
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**Principle**: MIDI CC11 (Expression) is the simplest `.rpp`-native sidechain. No REAPER-specific features, no binary envelope encoding, no ReaScript bridge. Pure MIDI standard — works with any synth (Serum 2 confirmed).
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**Data flow**:
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```
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Drumloop WAV
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→ DrumLoopAnalyzer.analyze() → transient_positions("kick")
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→ beat-positions cache (dict[str, list[float]])
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→ build_bass_track(sections, offsets, key_root, key_minor, kick_cache={})
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→ generates CCEvent objects {controller=11, time, value}
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→ ClipDef.midi_cc = [...]
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→ RPPBuilder._build_midi_source() emits E-lines
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```
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**CC11 ducking shape per kick hit** (all times in beats relative to clip start):
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| Offset from kick | CC11 Value | Description |
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|-----------------|------------|-------------|
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| kick_time | 50 | Instant dip (~-9dB) |
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| kick_time + 0.02| 50 | Hold through transient |
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| kick_time + 0.18| 127 | Release complete (80ms ≈ 0.16 beats) |
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**Key decision — MIDI CC11 vs alternatives**:
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| Option | Verdict | Why |
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|--------|---------|-----|
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| **A: MIDI CC11 (Expression)** | ✅ Chosen | `.rpp` MIDI source format supports `E B0 0B xx` lines. Serum 2, most synths respond. Trivial builder change. |
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| B: Track volume envelope (VOLENV2) | ❌ Rejected | Binary/chunk encoding in `.rpp` — fragile, hard to debug, no benefit over CC11 for this use case. |
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| C: ReaScript ReaComp sidechain | ⏸️ Deferred | Works only in Phase 2 with REAPER running. Use as future enhancement for non-MIDI audio basses. |
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## Affected Areas
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| Area | Impact | Description |
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|------|--------|-------------|
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| `src/core/schema.py` | Modified | Add `CCEvent` dataclass (`controller`, `time`, `value`); add `midi_cc: list[CCEvent]` to `ClipDef` |
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| `scripts/compose.py` | Modified | Add `_get_kick_cache()`, pass to `build_bass_track()`, generate CC11 events in bass clips |
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| `src/reaper_builder/__init__.py` | Modified | `_build_midi_source()` interleaves CC events into E-line stream |
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| `src/composer/drum_analyzer.py` | Unchanged | Already exports `transient_positions("kick")` — zero changes needed |
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| `tests/test_compose_integration.py` | Modified | Verify CC events present in bass clips, correct CC11 values at kick positions |
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| `tests/test_reaper_builder.py` | Modified | Verify `_build_midi_source()` emits `B0 0B` E-lines |
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## Risks
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| Risk | Likelihood | Mitigation |
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|------|------------|------------|
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| Synth doesn't respond to CC11 | Low | Serum 2, Omnisphere, Diva all support it. Add `_CC11_VOLUME_MIN` constant for easy disable (set to 127 = no ducking). |
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| DrumloopAnalyzer misclassifies kick transients | Med | Only use transients with `confidence > 0.6`; add `KICK_CONFIDENCE_THRESHOLD = 0.6` constant. |
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| CC events overlap MIDI notes in E-line stream | Low | Sort all events (notes + CC) by absolute time; REAPER E-lines are monotonic delta-encoded. |
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## Rollback Plan
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Delete `midi_cc` from `ClipDef` and revert builder to skip CC events. Remove `_get_kick_cache()` from compose.py. No schema migrations needed — `midi_cc` defaults to empty list (zero behavioral change). One-commit revert.
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## Dependencies
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- `librosa` (already a project dependency via `drum_analyzer.py`)
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- `DrumLoopAnalyzer` (already implemented and tested)
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- No new packages, no external APIs.
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## Success Criteria
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- [ ] Bass MIDI clips contain CC11 (Expression) E-lines at kick hit positions
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- [ ] CC11 value drops to ~50 at kick onset, recovers to 127 within 0.18 beats
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- [ ] DrumLoopAnalyzer correctly identifies kick transients in all 5 drumloop variants
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- [ ] Kick position cache avoids re-analyzing same WAV across sections
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- [ ] 110 existing tests pass unchanged
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- [ ] `.rpp` output opens in REAPER without errors; bass audibly ducks when kick hits
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- [ ] `validate_rpp_output()` reports no regressions
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