Re: music function to be included somewhere in scm/*

[Alexander Kobel]

Hi Urs, hi all.

On 2016-12-14 11:18, Urs Liska wrote:
> Am 14.12.2016 um 10:43 schrieb Alexander Kobel:
> > > To allow automated creation of lyric extenders a helper function is
> > > needed
> >
> > ... that does exactly this, adding extenders everywhere.
> >
> > IMHO, the actual question to decide upon is: Do we want this to be
> > enabled by default? IIUC, the fact that extenders are not automatic is
> > a known shortcoming. NR 2.1.1 states under "Known issues and warnings":
> > "Extender lines under melismata are not created automatically; they
> > must be inserted manually with a double underscore." (see
> > http://lilypond.org/doc/v2.19/Documentation/notation/common-notation-for-vocal-music#multiple-notes-to-one-syllable)
> >
> >
> > With Knut's patch, this will mostly impact scores where extenders are
> > left out unintentionally. Still, it will be a burden for convert-ly
> > unless we have a global (or per lyric definition) \noAutomaticExtender
> > rule that is inserted by default.
> >
> > On the other hand, there is the chance to get rid of scores where
> > users don't add extenders simply because they are not aware of their
> > importance or the proper syntax.
>
> My gut feeling says: Yes, this is an improvement and should be there by
> default. IIUC the reason why this has to be discussed is because that
> could change/break existing scores, right?

Correct. Change: yes, for sure; break: hardly, unless non-standard 
adjustments to lyrics have been made.

> If so, could you please think about an example where the patch would
> have a negative impact that can't reasonably be caught by convert-ly?
> Just because you two are much more into the topic, so that could help us
> others understand ...

The only difficult situation for an automatic conversion that I can 
think of is the following:
Attached is a modified version of the "divisi lyrics" example from NR 
2.1.2, along with a modified version of \autoextenders that alleviates 
the severity and offers a way out. The file features a slightly 
different approach to divisi lyrics, where the second voice persists 
over the entire length of music, but some notes are skipped in the 
lyrics with _.

The short stub extenders after "We" and in the third lyrics line will be 
removed by Knut's patch, so they are not a problem (the picture is made 
from an unpatched Lily version). The issue is with the long extenders 
after "will" without corrections. That's because the several _ _ in the 
lyrics create a melisma over several notes, which is semantically wrong, 
but visually indistinguishable from the correct semantics; hence, I 
could imagine that this notation has been used in several scores with 
divisi lyrics. I'm no exception myself.

My guess is that a convert-ly rule that translates every occurence of
   word _
to
   \once \override LyricText.self-alignment-X = #LEFT word \markup{\null}
or
   \once \override LyricText.self-alignment-X = #LEFT word ""
will be sufficient to resolve it, but I'm not sure how robust this 
approach is. This fakes the melisma by left-alignment, but semantically 
leaves "word" assigned to only one note.
"" gives a warning "LyricText has empty extent and non-empty stencil.", 
though; for the more verbose \markup{\null} I can't figure out how to 
leave out the braces: \markup \null translates to (markup #:null) in 
Scheme, but the Scheme construct (markup #:null) creates (markup #:line 
(#:null)) somewhere on the way, and those don't compare equal...


For "normal" lyrics, it's difficult to tell. I cannot imagine a 
"negative" impact in the sense that readability is affected for proper 
lyrics. But at least there is a change.

E.g., I took some (more or less) random piece from CPDL - have a look at
   http://www.uma.es/victoria/pdf/Cum_Beatus_Ignatius.pdf
A typical renaissance piece with typical notation (no slurs). Alvarez is 
clearly aware of extenders and uses them, e.g. in m. 43. However, he 
decided not to add them at other places, e.g. for the very first word of 
the canto or in the final bars m. 100 - 102. I guess that this is 
deliberate decision and not lazyness, and the same is done throughout 
his other scores.

I could e.g. imagine that some editor distinguishes for { b2~ | b r } in 
m. 53: with extender, hold the entire value of the note; without, you're 
allowed to stop earlier, e.g. on the barline. Not saying that this is 
Alvarez' intention, or that this is a good or bad interpretation, but 
you never know. At least, it would be an explanation for having 
extenders only here and there.


But I'm confident that in most cases (basically, short of misusing 
lyrics for other means), the changes will not deteriorate the appearance 
and readability, rather the contrary.


Cheers,
Alexander

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divisi.ly
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