# Rivet 0.2 implementation plan

## Musical intent
Develop a producer's own motif through audible choices about recognition, space,
contrast, and return. Offer three distinct compositional proposals rather than
three randomly shifted versions. Emotional interpretation stays with the producer.

## Engine
- Keep an exact opening quotation. Build subsequent two-bar sections as statement,
  answer, departure, and return (four-bar phrases use statement and return).
- Add tasks Develop, Answer, Make space, and Return. Generate a deterministic pool
  using rhythmic displacement, fragmentation, call/response, sparse subtraction,
  a later register peak, changed endings, and harmonic returns; remove duplicates
  and choose three candidates by task fit and musical distance. Return fewer if
  locks make three distinct outcomes impossible.
- Preserve groove and contour independently. Per-note locks protect pitch, rhythm,
  or every attribute. Locked events survive subtraction; rhythm locks keep exact
  timing and duration. Global constraints and locks take precedence over transforms.
- Optional harmony consists of bounded time regions with pitch-class masks and
  bass pitch. Accept polyphonic MIDI without claiming chord-root detection. Also
  provide editable per-bar chord progressions. Guide metrically strong notes and
  ending targets using the actual harmony at that time. Open endings prefer an
  available scale tone outside the ending chord; closed endings use chord tones.
- Candidate generation changes note count, spacing, duration, and articulation
  when constraints allow. Preserve recognizable fragments; avoid overlaps and
  clipping MIDI values. Keep generated notes within two-bar section boundaries so
  sections can be combined safely.

## Producer workflow
Import motif -> choose identity/locks -> optionally import or enter harmony ->
choose task -> audition alternatives -> pin two-bar sections -> export combined
MIDI or accept a complete candidate. Retain accepted work during regeneration.
Pins survive changes to task and seed, and clear when source or phrase length
changes. Pinned material overrides regenerated sections. Reject unsafe seams
rather than silently truncate a sustained note.

## Audition
Keep the internal voice and add a MIDI output mode. Preview is explicitly started,
optionally loops, and switches pending selections at the next two-bar boundary or
current clip end. Stop, replacement, mode changes, reset, and state restoration
release emitted notes. Host transport start never auto-starts audition. All clips,
queues, scheduling, and MIDI event emission remain bounded and allocation-free
on the audio thread. Validate FL Studio routing manually; retain MIDI file export
as the reliable commit path. Native OS MIDI drag-out is outside this release.

## Compatibility and verification
Write state version 2; migrate version-1 JSON and host fields with serde defaults,
retain legacy strategy names for old candidates, and keep the persisted host field
identifier. New controls/harmony/pins/audition choices persist. Test timing, locks,
contour, harmonic targets, candidate diversity, section composition, migration,
loop boundaries, sample-accurate note events, queued switches, and RT allocation.
Run existing core/ABI tests and Clippy, render the updated editor, and package
Windows CLAP plus Linux CLAP/standalone. Do not claim Devath-derived algorithms or
FL Studio validation without direct evidence.