JamPilot 1.4.2 — the fifth needs a bass player, the pickup note lets go of the chord

The theme of this release: the root. Two fixes for the same symptom
seen from two sides: a slash chord on the chip and a big "A over D" in the
bass view where the band plays plain D. One comes from a guitar voicing,
the other from the bass player's own pickup note — and neither should
reach the screen. Every number below is measured, the tables live in
tests/reference/README.md and tests/realaudio/.

The fifth in the bass needs a bass player

In the first verse of If This Is Goodbye (Knopfler/Harris) nobody plays
bass. The lowest string under the D shape is the open A (110 Hz); the
guitar's D sits an octave above the low band. The low band therefore reads
A, and every D of the verse came up as D/A — eight bars out of eight, in
bass mode as a big A over D. The ratio hurdle from 1.4.0 cannot help
here: there is no root below to compare against. Same class as D/A over
every D in Eight Days a Week and D6/A in It's Too Late.

The fifth is the only chord tone a guitar shape puts under the root by
itself; a third or a seventh in the bass is always deliberate. So only the
fifth now needs proof a guitar cannot give: at least 5 % of its low-band
energy in the bass register C1–D♯2 (32–78 Hz, below the low E string).
Without that proof the chord stays in root position. The real A pedal the
bass holds under D later in the same song (A1, 55 Hz) passes.

Offline on the reference set nothing moves (1 false slash in 385 chords,
11 of 27 inversions, unchanged). Live, fifth slashes before → after:
If This Is Goodbye 11 → 2, Let It Be 7 → 5, Something 8 → 7,
It's Too Late 10 → 10 (a bass plays there, the fifth does sound in the
register). A general register gate for every slash tone was measured and
rejected: it takes ten of the eleven inversions, because the bass
fundamentals of sixties recordings rarely reach below E2
(tests/realaudio/REPORT_if_this_is_goodbye.md).

The pickup note no longer sticks to the chord

Sailing to Philadelphia in bass mode showed E over F#m7 at the start
of every form, although the bass plays a clear F# from the downbeat on.
The chain: the bass plays an E pickup before the downbeat. The boundary
refinement pulls the F#m7 onset 0.3 s early onto that pickup (E is a chord
tone). The model sets F#m7 only on the downbeat and still says A at the
commit line, so the late-boundary rule from 1.1.0 enters A as a 50 ms blip
and F#m7 a second time. The blip rule from 1.4.1 keeps both out of the
events — but the blip has already cut the committed chord's bass window
from two seconds to a quarter second: exactly the pickup. There E is the
majority, E is a chord tone, and it lands on the event for good.

The late-boundary rule now recognises this as the same chord change, set
later by the model than by the refinement, and enters nothing: when the
re-reported chord is the one before the last committed event, the model
immediately leads the committed chord again, and its onset lies at most
0.75 s behind. No onset moves; a genuine D – A – D with a longer A is
still added as before.

Measured on the live path: Sailing loses all three F#m7/E and six
other wrong slashes (A/C#, D/F#, E/B) and gains nine bass roots. On
the reference set event count, timing, beats and bass-only hits are
unchanged, and the unannotated slashes go away: It's Too Late 15 → 1
(the D/A over every D6 known since August was the Am7 bass in the stub
before the downbeat), Crazy Little Thing 10 → 3, Let It Be 7 → 6;
Something gains the annotated G/D at 3.5 s. A minimum bass-window
length as a second hurdle was measured and rejected: no gain, costs the
roots of one-beat chords (tests/realaudio/REPORT_sailing_to_philadelphia.md).
The pickup fix was judged in the rehearsal room (Sailing to Philadelphia,
Telegraph Road); the fifth rule is measured on recordings so far.

Smaller things

• Comfortably Numb (PULSE live version): the passing bass from 1.4.1 hits
  4 of 13 solo transitions; the rest are a too-short F# run or an F#m
  label from the model. Left as it is — Moises shows plain G → Em there
  too (tests/realaudio/REPORT_comfortably_numb.md).
• 648 tests (1.4.1: 633).