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.
78 lines
3.2 KiB
Markdown
78 lines
3.2 KiB
Markdown
# Proposal: transitions-fx
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## Intent
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9 sections play back-to-back with zero transition — the song feels like disjointed loops. Add transition FX (risers, impacts, sweeps) at section boundaries to glue sections into a coherent arrangement.
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## Scope
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### In Scope
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- Place transition FX clips (audio samples) on a dedicated "Transition FX" track at section boundaries
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- Riser/wash FX: 2–4 beats before section changes (e.g., build → chorus drop)
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- Impact/hit FX: on the downbeat of CHORUS, FINAL, VERSE2 entries
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- Filter sweep simulation via fade-in/fade-out on adjacent clips
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- Transition plan: which boundary gets which FX type + duration
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- Reuse existing FX-role samples from library (impacts, risers, transition FX, wash)
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### Out of Scope
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- Synthesized FX generation (numpy waveform synthesis) — deferred to future
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- MIDI CC filter automation in RPP (no CC support in builder today)
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- Per-track volume automation curves
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- Reverse cymbal (no suitable samples in library)
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## Capabilities
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### New Capabilities
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- `transition-fx`: Placement of audio FX clips at section boundaries for arrangement glue
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### Modified Capabilities
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None — existing section/track structure unchanged.
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## Approach
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**Audio samples from library** — the library has 57 FX-role samples including:
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- Impacts: `fx_C2_126_boomy` (2.5s, from `impact.wav`)
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- Risers: `fx_C#5_123_aggressive` (30s), `fx_G3_143_boomy` (6.6s, "RISER 3")
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- Transition FX: 4 "transicion fx" variants (1.0–1.7s)
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- Wash/noise: `fx_G#6_136_aggressive` (3.3s)
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- Short shots/gates: "CAMTAZO 1–2" (1.5–2.0s), "PUERTA" (0.2s)
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Place audio clips on a new "FX" track at section boundaries:
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- **Riser/wash**: starts 2–4 beats BEFORE boundary, ends on boundary downbeat
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- **Impact**: starts on boundary downbeat, short duration (1–2 beats)
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- Use existing `fade_in`/`fade_out` on ClipDef for filter-like sweeps
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- Use SampleSelector with `role="fx"` to pick compatible samples
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## Affected Areas
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| Area | Impact | Description |
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|------|--------|-------------|
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| `scripts/compose.py` | Modified | Add `build_fx_track()` — places FX clips between sections |
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| `src/core/schema.py` | Unchanged | `ClipDef` already has `position`, `length`, `audio_path`, `fade_in`, `fade_out` |
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| `src/reaper_builder/__init__.py` | Unchanged | Audio clip building already works |
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## Risks
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| Risk | Likelihood | Mitigation |
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|------|------------|------------|
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| FX samples may not match project key | Low | FX role is ATONAL_ROLES — key scoring skipped by selector |
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| Long riser samples exceed needed duration | Low | Clip length sets playback window; sample trimmed automatically |
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| No suitable riser for specific boundary | Med | Fall back to fade_in on next section clip |
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## Rollback Plan
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Remove `build_fx_track()` call from `main()`. Existing tracks untouched.
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## Dependencies
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- `data/sample_index.json` (already exists)
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- `SampleSelector` with `role="fx"` (already works)
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## Success Criteria
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- [ ] `python scripts/compose.py --bpm 99 --key Am` produces .rpp with FX clips at section boundaries
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- [ ] At least one FX clip between: build→chorus, chorus→verse2, bridge→final, outro end
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- [ ] FX clips have appropriate fade_in/fade_out curves
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- [ ] 110 existing tests continue to pass
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- [ ] Song renders without gaps — FX clips overlap/bridge sections
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