Accidental style with brief changes of clef.

[Nick Bailey]

I'm aware that this has been discussed before at https://lists.nongnu.org/archive/html/lilypond-user/2015-10/msg00678.html and https://lists.nongnu.org/archive/html/lilypond-user/2015-10/msg00668.html but we are busy engraving a performance edition of a composer who routinely expects scores like this:

\version "2.22.0"
\score {
  \new Staff
    { \clef bass cis'4 \clef treble cis' \clef bass cis' }
  \layout {}
}

_not_ to have a sharp sign on the final note. The desired outcome is that a new clef does get an accidental but that when the melodic line returns to the bass clef, the accidentals from the original bass clef in the same staff and bar are retained. You would see #C #C C on the paper. Apparently, this practice is particularly common in keyboard scores which traverse a large distance up and down the keyboard, changing clefs twice in the same bar. In some conventions, it's as if the second bass clef indicates a return to the accidentals current just before the treble clef rather than just forgetting them all. This is news to me, but I've not been writing and performing piano music for decades.

This isn't a question about whether that's "right"; I understand the choice of behaviour for the accidental styles based on the statement in Gould's book. The question is how best to achieve it. Currently we'd enter \once \omit Accidental before the final notes/chords (which I suppose could be abbreviated). This isn't convenient, rendering the input file too verbose, and is error prone because if a note is changed a required accidental might be omitted by mistake.

What would be really nice would be either to have a custom accidentalStyle, or else an easy way of omitting the accidental which is part of the note by adding a suffix, so that in the same way cis! forces the accidental to appear, cis@, for example, forces it not to. Either of these strike me as something quite major, but I thought I should canvas opinion on the list in case they aren't. Or perhaps they've already been done.

Here's a less-than-minimum working example some real music to show where accidentals are deliberately omitted at the moment beginning and ending in the treble clef, 4/4 time. Without the \omits, the last beat is full of repeated naturals in any of the accidentalStyles I know about.

%measure 2 ==========================================
<f ces' des>16 \mp <ces ees aes> <aes des f> <f aes ces>
\clef bass <des ees aes> <aes ces f> <f aes des> <ces des aes'>
<f aes des> <aes ces f> <des ees aes> <f aes ces>
\clef treble \once \omit Accidental <aes des f>
\once \omit Accidental <ces ees aes>
\once \omit Accidental <f ces' des> <aes ees' f>