Remix

Consult the library snapshot — lightly. Read tools/composition-index/snapshot.txt — the pre-rendered digest the PostToolUse hook keeps current. Remixes are inherently specified (source + target genre), so the snapshot's role here is narrower than in /compose:

• Look at the primary-genre distribution and top tags. Is the target genre already overrepresented in the library? If yes, consider a less-overused sub-variant — e.g. for a "trance" request with three trance tracks already, lean toward progressive-trance, psy-trance, or uplifting-trance rather than another generic four-on-the-floor.
• Glance at the Library gaps section. If the target genre itself shows up as a gap, that's a free signal to commit to the request without second-guessing — the library is actively missing it.
• Do not override the user's explicit target genre. The snapshot is for sub-variant flavor, not redirection.

Silent integration — do not verbalize the snapshot reasoning to the user in the final response. The snapshot already excludes verification fixtures tagged demo.

Load target-genre reference. Always read:

• .claude/skills/compose/gm-samples.md — for any sampled instruments
• .claude/skills/compose/genre-guide.md — for target-genre conventions

If the target genre is one of house, bass house, dubstep, drum & bass, future bass, or trance, also read:

• .claude/skills/compose/genre-templates.md — and use the target genre's template as a sound-design starting point

If the target involves synths, effects, modulation, or one-shot drums, also read:

• .claude/skills/compose/synth-presets.md
• .claude/skills/compose/effects-reference.md
• .claude/skills/compose/modulation-patterns.md
• .claude/skills/compose/oneshot-hits.md

Plan the transformation. Decide before writing any notes:

• Tempo. Adopt the target genre's natural BPM unless the source is already in range. Document the change.
• Instrument swap table. For each source instrument, pick a target-genre equivalent (role-preserving: bass→bass, pad→pad, lead→lead). Drop instruments that don't fit; add ones the genre requires (e.g., supersaw lead + arp pluck for trance).
• Drum rework. Target genre's drum pattern, not the source's. Four-on-the-floor for house/trance; half-time for dubstep; breakbeat for DnB.
• Effects/modulation. Master chain, sidechain routes, automation lanes — pulled from the genre template, not the source.

Preserve these exactly.

• metadata.key
• Section names, order, and bar counts
• Chord progression per section (root + quality; voicings can change)
• Overall energy arc (if source has a drop at section 4, the remix drops at section 4)

Rework these freely.

• metadata.bpm, metadata.title (append " (Genre Remix)" or similar)
• metadata.tags — new primary tag (target genre) first, followed by remix-relevant modifiers. Optionally include "remix" and a reference to the source genre as a modifier (e.g., ["trance", "remix", "dubstep-source", "uplifting"]).
• instruments[] — new list per the swap table
• Every track's notes — re-voiced for the new instruments, re-rhythmed for the new genre, but constrained to the preserved chords
• Melodies: re-compose over the same changes in a genre-appropriate style. Don't transplant the source melody verbatim — a trance lead moves differently than a dubstep growl even over Fm–Db–Ab–Eb.
• masterEffects, automation, lfos, modulation, sidechain

Generate the composition JSON. Follow composition-format and music-theory rules. Every note written out — no placeholders. Vary velocity. Keep instruments in their natural registers (bass C1–G3, melody C4–C6, pads C3–G5).

For long remixes or heavy genre reworks, reach for the helper library at tools/compose-helpers/ for repetitive scaffolding (drum grids, bass patterns, pad sustains, arpeggios, humanization). Write a throwaway scratch script that imports primitives, builds repetitive tracks, and leaves melodies and fills hand-written. Helper output is a starting point — hand-edit for expression. New helpers are encouraged if a primitive you need doesn't exist yet.

Rigidity pass. Before finalizing, scan the generated remix for mechanical uniformity and adjust. Applies regardless of whether helpers were used:

• Velocity uniformity: if >60% of notes in a track share the same velocity, apply a natural velocity curve (emphasize downbeats, soften offbeats, ghost notes between hits).
• Bar-to-bar identicalness: if 4+ consecutive bars are literal duplicates within a track, introduce one variation — a ghost note, a dropped hit, a velocity accent, a one-bar fill.
• Section contrast: each section should have at least one distinguishing element from its neighbors (instrumentation, density, dynamics, register, drum variation).
• Transition markers: every section boundary should have some audible marker — fill, crash, drop-out, sweep, automation point. Add one if none exist.

Write the JSON — draft-first. Author to /tmp/composition-draft-<source-stem>-<genre-slug>.json throughout generation. Validate against the schema. Then run pnpm finalize-composition <source-stem>-<genre-slug> as the final step (e.g., pnpm finalize-composition subterra-trance) — the helper copies the draft to compositions/<source-stem>-<genre-slug>.json and updates the composition index in one atomic operation. Do not overwrite the source composition. See .claude/rules/composition-drafts.md for the full convention and rationale.

Describe the remix briefly. New title, new BPM, instrument swap summary, what was preserved, and what the rigidity pass adjusted (or "rigidity pass clean" if no adjustments were needed). A few sentences max.