Task #33 asked "does every OPAL track have a riser, and are they harmonized?".
Answering it needed the setlist (backlog.md § OPAL 2026, 12 tracks with BPMs)
resolved to actual .tidal files, then every d10 / riser / sweep / impact hit read
in context. Result is worse than expected and worth having in writing before
rehearsal rather than discovering it on stage.

Findings:
- Only 2 of 12 tracks have a riser: Take Five Drops and Vague de CRIME.
- 5 tracks have d10 completely free (Bombe, WAP, Mafia, Sunshine, Desire) — a
  riser drops straight in.
- 4 tracks have d10 already occupied by non-riser material (Piment's "Menace",
  Perfect's euclidian arps, Gimme Acid's "GIMME THAT", Revolution's sweet
  trigger) — those need a different stream, not a d10 paste.
- Track 3, "Am i Doing it Right?", has NO .tidal file matching any slug I tried.
  Per the repo convention it must exist under a name I didn't guess. Flagged as
  an open question — the set is incomplete until it's found.

The two existing risers disagree with each other, which is the actual #33 problem:
Take Five sleeps 24 cycles and builds over the final 8 (a build-up INTO a drop),
while Vague de CRIME fires on cycle 1 of 8 at the sample's natural length (an
accent OUT of a downbeat). Same folder, opposite musical function — exactly the
muscle-memory hazard when you're moving track to track mid-set. Also caught: Take
Five's d10 is the only stream in the whole set with no gF/gM wrapper, so global
filters and mutes cannot touch it — reach for gF1 during that build and everything
ducks except the riser.

Proposed one house helper, `gRiser period build`, derived verbatim from PLN's own
working Take Five block rather than invented. loopAt is the load-bearing trick: it
makes the riser's length independent of the sample's natural length, so one helper
lands correctly from 120 to 166 BPM.

Validated the proposal two ways before recommending it, per build-the-katana-first:
- compiles clean against the real tidal-1.9.5 (ghc -fno-code, no stream started);
- the generated mask is BIT-IDENTICAL to the hand-written "<f!24 t!8>" — queryArc
  over cycles 0-32 gives exactly 24 False then 8 True for both, compared
  elementwise, mine == theirs -> True. It's a faithful refactor, not a lookalike.

Deliberately NOT committed to BootTidal.hs and NOT applied to any track: what the
grep cannot answer is whether stock gain 0.8 / room 0.4 sits right under a 166 BPM
liquid dnb track. That's ears. Suggested trial order is Desire (the FINALE, where a
missing build costs most), then Mafia and Sunshine (the set's peak).

Ties to #13: with default-xfade dN now baked in (98d073f2), every track launch
already blends over 4 cycles. A riser is the musical counterpart to that structural
crossfade — the xfade stops the seam being abrupt, the riser tells the room a
change is coming. Together they're what turn "ctrl+enter and pray" into a transition.