Re: Cross-staff beam slope - can it be specified?

[David Sumbler]

On Sat, 2017-10-28 at 08:49 -0400, Ben wrote:
> On 10/27/2017 1:33 PM, David Sumbler wrote:
> > In the above rather silly example, the beam between the 2 cross-
> > staff
> > notes slopes slightly upwards.  If I add a dynamic, say \f , after
> > <c'
> > g>2. in line 7, the staves are forced further apart, and the beam
> > slopes slightly downwards.
> > 
> > If I now add a further dynamic, say ^\p , to the lower staff after
> > <e
> > c>2. in line 9, the staves are forced still further apart and the
> > beam
> > now has a large downward slope.
> > 
> > The problem I have is that, in "real life", I don't know how far
> > apart
> > the staves will be because of the space requirements of other parts
> > of
> > the music.  Generally I would prefer to allow Lilypond to determine
> > where line ends etc. should be, so I don't even know which bits of
> > the
> > music will affect the slope of the beam.  And even if I did know,
> > an
> > alteration to the music in the closely preceding and following bars
> > might well affect the spacing of the staves and hence the slope of
> > the
> > beam.
> > 
> > Is there any way of ensuring that the beam always has a
> > predetermined
> > slope - say 10° downwards - and that the stem lengths will
> > automatically be adjusted to allow for this?
> > 
> > David
>  
> Hello,
> 
> Check out this older post here, it deals with cross beam slopes:
> http://lilypond.1069038.n5.nabble.com/Adjusting-beam-slope-with-cross
> -staff-notes-td140283.html
> 
> David Nalesnik wrote a function where instead of specifying the
> absolute values for positions, it allows you to indicate
> displacements from the values LilyPond would use by default.
> 
> It sounds like that's what you are looking for, does this help?

Thanks for your reply.  I have had a look at David's function, but it
doesn't seem to be suitable in this case.  It allows one to specify
vertical off-sets for the ends of a beam relative to the offsets
Lilypond would use by default.  But my problem is that those defaults
may change depending on spacing issues caused by changes in the music
in the few bars before or after the notes with the beam.

What I really need is some way of specifying the relative vertical
heights of the ends of the beam whilst leaving Lilypond to determine
the absolute vertical position.  If I had sufficient understanding of
the inner workings of Lilypond, I am sure that I could fairly easily
write the necessary Scheme code.  But I don't have that understanding,
so I shall have to make do with tweaking the beam position once the
rest of the music is absolutely finalized.

David