Re: Patch: figured bass. [Comments wanted]

[Juergen Reuter]

Just to avoid confusion:

Figured bass notation does not at all encounter harmonics, it just gives
fingerings relative to the bass note.  For example, if you have a chord
<c f a>, then the bass note "c" is engraved as note, and the fingering
numbers are:
6
4

In other words, I see two possibilities of syntax: either you specify all
notes like in <c f a>.  Then lily has to separate the bass note
(i.e. the deepest note) c from all other notes (in the example, f and a).
The c is printed, and the f and a result in figures 4 and 6 (as counted
relative to the c), respectively.  After that, you have to apply some kind
of normalization, that should be done in scheme.  For example, the figures
"3 5" are normalized into the single figure "5", since the "3" is, by
default, always played, unless it dissonates (as in "3 4", which will stay
"3 4" after normalization).  There are roughly a dozen of such
normalization rules.

The second possibility of syntax that I see is, as you already suggest, to
specify the bass notes separatly, maybe even as a separate \notes section.
Then, normalization has just to be applied to the \figure section, but for
performance, you have to encounter the \notes section, since the figures
are relative to the notes in the bass section.

Please also note that the conversion from figures to notes is not unique,
since it allows chord inversions.  The conversion from chords to figures
is, as far as I know, more or less unique.  "Less" means, that ornaments
are dropped when converting to figures; but they were anyway notated
sparsely in baroque music (which is the domain of figured bass).

With both possibilities of syntax, you need a reverse normalization for
performance.

Greetings,
           Juergen