Re: Reasons for cross-voice limitations?

[Urs Liska]

Am 30.03.2015 um 07:58 schrieb David Kastrup:
> Kevin Barry <address@hidden> writes:
>
> > For sure the voice context limitations are a pain, and if I knew how, I
> > would write a function for starting and finishing slurs without the need
> > for creating a hidden voice, but I don't even know if it is possible. In my
> > own head, I imagine that LilyPond `thinks' in voices and there isn't much
> > that can be done about that. Practically 100% of my work is either piano
> > music or music reduced to two staves, so I bump up against this issue all
> > the time. I never use the part combiner.
> You can move the slur engraver to Staff level and use spanner-id for all
> slurs.  But that will make you lose cross-staff slurs.  Of course, you
> can use the slur engraver to Score level, but then you really have to
> work your spanner-id variety.
>
> This would warrant a better mechanism to transplant spanners to a
> different context: basically one would want a mechanism to listen to
> slur endings in a different context than to slur starts.  Possibly
> optionally with a \once qualification.

I think the idea of an analogy to \change Staff would be a good start. 
Tell a slur that it is going to end in another voice, probably 
immediately before it is started. Maybe something like
  \once \override Slur.target = "another-voice-name"
or
  \once \override Slur.id = "my-changed-slur"
  \once \override Slur.change-voice = ##t.

The first one would require the target to be a named voice, the second 
would require all context to listen for that slur.

(of course slurs and co. are only one part of the issue, dynamics and 
text spanners share the problem).

Urs