Re: Problems regarding figured bass

[Reinhold Kainhofer]

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Am Sonntag, 14. Juni 2009 15:27:56 schrieb Carl D. Sorensen:
> On 6/14/09 3:38 AM, "Reinhold Kainhofer" <address@hidden> wrote:
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> > Hi all,
> > I'm running into several problems with figured bass while writing another
> > large
> > orchestral piece. Attached is a sample file highlighting these issues:
> >
> > 1) How can I add a figure above a rest? It works for skips, but a figure
> > assigned to a rest simply isn't printed at all... (see first vs. second
> > measure, where the same figured bass input is used!)
> > It works if I use \new FiguredBass for the figured bass, but I need the
> > figures
> > in the staff, since otherwise they are printed below and they align
> > vertically,
> > causing them to be too far away from the staff in most places.
>
> Have you tried ignoreFiguredBassRest?

Ah, thanks, I didn't know this.
I wonder, though, why this is set to ##f by default, since a figure on a rest 
means that the harmony starts a beat earlier than the bass note that follows 
(the harmony is derived from the following bass note, see e.g. the German 
Wikipedia). From what I can see, this is standard figured bass notation, but 
not mentioned anywhere in the docs...

> > 2) The figures don't collide with the notes themselves, but they collide 
> > with the articulations (trills, accents, staccati, etc.) How can I avoid
> > this?
>
> Extra-offset?

Extra offset has several problems:
1) One has to do this manually, in particular I have to check every figure for 
collisions, look it up in the lilypond file, determine a proper offset and add 
an override. 
2) Extra-offset is applied after all layouting has been done, so the staff 
spacing will be done and shifting the figures up afterwards will cause the a 
smaller vertical distance to the staff above than between the other staves...

I was rather looking for some way so that lilypond automatically detects such 
collisions as collisions. (I suppose the current collisions are a bug, right?)

> > 3) How can I draw a figure extender without an explicit starting figure
> > (I think
> > this means that the normal default triad should be held)? If I'm using
> >   s4 <_> <_> <_>
> > then I only get a warning message:
> > Programmierfehler: must have Item for spanner bound of
> > BassFigureContinuation
>
> Make an explicit starting triad with 'transparent = ##t ?

Alternatively, the Internals Reference says that there is a 
implicitBassFigures property of FiguredBass, which defines which figures are 
assumed to be implicit and hidden (but used for extenders!). Unfortunately, 
this only applies to the base figure, so one can define 5 to be an implicit 
bass 
figure (i.e. <5> <5> <5> will only produce an extender line but no 5), but then 
it's impossible to have an explicit 5 figure, which is what I would need, too.

Even worse, since the list only compares the base figure, figures like <5-> 
will 
still be interpreted as implicit, which is definitely not right.

As a workaround, one can define e.g. 100 (which is no bass figure to ever be 
found in a score) to be an implicit figure and use <100> <100> for an extender 
only. That's a bad hack, though, because the inherent meaning of the figures 
will be wrong (which is currently not a problem, because in visual output the 
internal representation is irrelevant. It might become relevant, though, if we 
ever add MusicXML export). 


I've added the solutions to the two solved problems to the LSR:
http://lsr.dsi.unimi.it/LSR/Item?id=606
http://lsr.dsi.unimi.it/LSR/Item?id=607

The remaining problems are now:
- -) Collisions of the figures with articulations
- -) How to draw a hat above a figure
- -) Inside a staff context, \markup does not work as a figure!!!

Cheers,
Reinhold
- -- 
- ------------------------------------------------------------------
Reinhold Kainhofer, address@hidden, http://reinhold.kainhofer.com/
 * Financial & Actuarial Math., Vienna Univ. of Technology, Austria
 * http://www.fam.tuwien.ac.at/, DVR: 0005886
 * LilyPond, Music typesetting, http://www.lilypond.org
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