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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: transitions-fx

Intent

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.

Scope

In Scope

Place transition FX clips (audio samples) on a dedicated "Transition FX" track at section boundaries
Riser/wash FX: 2–4 beats before section changes (e.g., build → chorus drop)
Impact/hit FX: on the downbeat of CHORUS, FINAL, VERSE2 entries
Filter sweep simulation via fade-in/fade-out on adjacent clips
Transition plan: which boundary gets which FX type + duration
Reuse existing FX-role samples from library (impacts, risers, transition FX, wash)

Out of Scope

Synthesized FX generation (numpy waveform synthesis) — deferred to future
MIDI CC filter automation in RPP (no CC support in builder today)
Per-track volume automation curves
Reverse cymbal (no suitable samples in library)

Capabilities

New Capabilities

transition-fx: Placement of audio FX clips at section boundaries for arrangement glue

Modified Capabilities

None — existing section/track structure unchanged.

Approach

Audio samples from library — the library has 57 FX-role samples including:

Impacts: fx_C2_126_boomy (2.5s, from impact.wav)
Risers: fx_C#5_123_aggressive (30s), fx_G3_143_boomy (6.6s, "RISER 3")
Transition FX: 4 "transicion fx" variants (1.0–1.7s)
Wash/noise: fx_G#6_136_aggressive (3.3s)
Short shots/gates: "CAMTAZO 1–2" (1.5–2.0s), "PUERTA" (0.2s)

Place audio clips on a new "FX" track at section boundaries:

Riser/wash: starts 2–4 beats BEFORE boundary, ends on boundary downbeat
Impact: starts on boundary downbeat, short duration (1–2 beats)
Use existing fade_in/fade_out on ClipDef for filter-like sweeps
Use SampleSelector with role="fx" to pick compatible samples

Affected Areas

Area	Impact	Description
`scripts/compose.py`	Modified	Add `build_fx_track()` — places FX clips between sections
`src/core/schema.py`	Unchanged	`ClipDef` already has `position`, `length`, `audio_path`, `fade_in`, `fade_out`
`src/reaper_builder/__init__.py`	Unchanged	Audio clip building already works

Risks

Risk	Likelihood	Mitigation
FX samples may not match project key	Low	FX role is ATONAL_ROLES — key scoring skipped by selector
Long riser samples exceed needed duration	Low	Clip length sets playback window; sample trimmed automatically
No suitable riser for specific boundary	Med	Fall back to fade_in on next section clip

Rollback Plan

Remove build_fx_track() call from main(). Existing tracks untouched.

Dependencies

data/sample_index.json (already exists)
SampleSelector with role="fx" (already works)

Success Criteria

python scripts/compose.py --bpm 99 --key Am produces .rpp with FX clips at section boundaries
At least one FX clip between: build→chorus, chorus→verse2, bridge→final, outro end
FX clips have appropriate fade_in/fade_out curves
110 existing tests continue to pass
Song renders without gaps — FX clips overlap/bridge sections

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