Re: "Slash" in figured bass

[Lukas-Fabian Moser]

Hi Werner,
> >  From Förster's book:
> > https://www.digitale-sammlungen.de/view/bsb10527178?page=64 ex. 141
> > I also attach an example from his "Practische Beyspiele", in which a
> > slightly different layout is being used in which the slash and the
> > figure are put separately over their respective notes.
> >
> > Of course it wouldn't be hard to cook up a solution (using \markup
> > in figures) for both styles, but I'd like to do it "the right way":
> > Do we already have a suitable slash symbol? If not, how should it be
> > designed?  Has anybody of you already used this symbol?
> I haven't seen this before, and I believe this is an ad-hoc invention
> of Förster for pedagogical purposes.  In particular, there is no
> fitting glyph in the SMuFL specification (AFAICS).  Consequently, a
> simple `\markup` solution is probably the way to go.

Adding some context:

The slash is pronounced the best of several possibilites by C. Ph. E. 
Bach ("Versuch über die wahre Art das Clavier zu spielen", Part II, Ch. 
1, § 76). See also the discussion in F. T. Arnold, "The Art of 
Accompaniment from a Thorough-Bass" (1931), Ch. XIX ("The Figuring of 
Transitional Notes", § 5 "Different methods of indicating 'transitus 
irregularis' in the Bass".

I'll think about adding the variants listed by Bach to LilyPond proper. 
For the time being, and for the sake of completeness, here's what I did, 
which is a bit makeshift design-wise, but the syntax seems nice to me:

\version "2.24.0"

slashMarkup = \markup \raise #-0.25 { " /" } % TODO: Paint decent glyph :-)

Slash_figure_engraver =
% Convert <_/> figure to slash slashMarkup
#(lambda (ctx)
   (make-engraver
    (listeners
     ((bass-figure-event engraver event)
      (when
       (and (null? (ly:event-property event 'figure))
            (null? (ly:event-property event 'text))
            (ly:event-property event 'diminished #f))
       (ly:event-set-property! event 'diminished #f)
       (ly:event-set-property! event 'text slashMarkup))))))

\layout {
  \context {
    \Score
    \consists #Slash_figure_engraver
  }
}

<<
  \new FiguredBass \figuremode {
    <_/> <6> <_/> <6>
  }
  \new Staff \with { \clef bass } {
    f4 e d c
  }
>>

(The even friendlier syntax variant </> would require changing the 
lexer/parser, I think.)

Lukas

CPE Bach.png
Description: PNG image