PLN, mid-rehearsal on the last speaker session before OPAL: "atm when i work
the track and change eg. a # gain 1.4 to # gain 1.5, it goes whole track all
d1-d12 through fadedown-fadeup over a few bars?? its not ok, i cant adjust
anymore." Then the good question: "fade d1 X -> d1 X should be constant, as
each percent of volume removed from X is added to id?"

He is right about the arithmetic and the rig breaks it in three places.

WHY CROSSFADING A PATTERN WITH ITSELF DIPS

  1. envEq/envEqR are EQUAL-POWER envelopes, g(t) = sqrt(sin(pi/2*t)), so
     g_in^2 + g_out^2 = 1. Correct — for a LINEAR gain stage.
  2. SuperDirt's law is amp = gain^4. At the midpoint both sides sit at
     g = sqrt(0.7071) = 0.8409, so each half's amplitude is 0.8409^4 = 0.5
     EXACTLY. The equal-power promise was made in the wrong domain.
  3. `overlay` fires the same sample TWICE. Two coherent voices would sum
     0.5 + 0.5 = 1.0 and be flat — that is PLN's model. What actually happens:

       orbit with `# cut N`   2nd voice releases the 1st (playSynths broadcasts
                              the cut group BEFORE amplitude is read — the same
                              mechanism as the 2026-07-29 ghost bug), one voice
                              survives at amp 0.5              => -6 dB
       orbit without cut      two independent voices, incoherent sum,
                              sqrt(.5^2 + .5^2) = 0.707        => -3 dB + comb

Deepest at t/2, unity again at t. With t=4 that is a four-bar swell on twelve
orbits at once — because each dN is its own transition and ctrl-enter re-sends
the whole blank-line-delimited block, all starting at the same `now`. Editing
one `# gain` changes one line but evaluates twelve.

THE STANDING CONCLUSION: an overlap crossfade can NEVER be transparent on a
cut-group orbit. `cut` means "one voice in this group"; a crossfade means "two".
Shortening the fade does not remove the dip, it makes it a blip instead of a
swell. The dip-free answer is a NON-overlapping transition (`clutchIn`), which
changes the feel of every seam in the set — so it waits for after OPAL (#13).
This file's own comment guessed that in July; it is now measured, not guessed.

CHANGES

- xfade default 4 -> 1 cycle. One token, so it is one token to flip back.
- xfadeCutIn gains a `t <= 0` branch returning the incoming pattern untouched.
  Needed before "0 = instant" can ever be offered: Tidal guards
  `_slow 0 _ = silence`, and `q |* gain silence` then has no right-hand values
  to match, so the INCOMING pattern comes out EMPTY. Unguarded, "0 cycles"
  means silence, not instant. Now `xfadeIn N 0 $ ...` is a real instant swap.
- Killed a trap in this file's own guidance: it recommended `p N $ ...` for fast
  iteration. `p` carries no `|< orbit`, so the sound lands on orbit 0 — wrong
  LCXL column, wrong Ardour stem, fader that looks dead — the exact failure the
  lines above it warn about. Points at `jumpTo N` / `xfadeIn N 0` instead.

VALIDATION: tools/check-boot.sh (safe mid-set, never grabs 6010) — helper block
typechecks against tidal-1.9.5, all 13 g* helpers audible with an untouched
controller, and the transition ghost check still reports 0 outgoing onsets after
the fade. Takes effect at the next Tidal boot; nothing in the running session
changed.