Re: \tag can't follow \lyricsto

[Nicolas Sceaux]

Le 16 juil. 08 à 13:31, Roman Stawski a écrit :

> The command order I'm using is from a really old template that I've
> been using for years without problems. I came across your formulation
> when checking an answer to another post on the bugs list.
>
> Looks as if I'll have to update my templates. (Who's got the sed user
> guide?)

You don't have to. The way you're using it is valid.
You just have to adapt it when using \tag to workaround the parser
defect.

> > However, there is an easier way to include or exclude
> > the harmony, without using tags, like this:
> >
> >
> > harmony = { \new Staff {a'1} }
> > <<
> > \new Staff { \new Voice = "dirge" { c''1 } }
> > \lyricsto "dirge" \new Lyrics { Whoops }
> > %\harmony %uncomment to include harmony
> > >>
>
> That doesn't convince me.

It was poor advice, your use of \tag is correct in this situation.

> Ideally, I want to produce different output from the same score
> _without_ touching the contents. My idea (dream?) of using tags was
> to eventually write a dollop of scheme that would be able to look at
> the command line arguments and set \keepWithTag or \removeWithTag as
> appropriate. However, the way that tags are implemented today isn't
> powerful enough for what I want to do... they can only be used to  
> filter
> music expressions -- I'd like to be able to filter out markup,  
> scores and
> anything else in the input file. (Well, I did say 'dream'!).
>
> At the moment I'm using a cobbled together solution partly based on  
> tags,
> and partly based on a perl preprocessor that does the filtering before
> passing the input onto to Lilypond -- but pretty it ain't.

You can conditionnaly insert music using a music function.
For instance:

#(define (true-function . args) #t)
insertWhen =
#(define-music-function (parser location condition music) (true- 
function ly:music?)
   (if condition
       music
       (make-music 'Music)))

<<
  \new Staff { \new Voice = "dirge" { c''1 } }
  \lyricsto "dirge" \new Lyrics \lyricmode { Whoops }
  \insertWhen #(eqv? (ly:get-option 'part) 'harmony) \new Staff { a'1 }
>>

Then, when compiling your input file with -dpart=harmony option,
the staff is added.

You can also specialize \insertWhen, the following way:

insertWhenHarmony =
#(define-music-function (parser location music) (ly:music?)
   (if (eqv? (ly:get-option 'part) 'harmony)
       music
       (make-music 'Music)))

<<
  \new Staff { \new Voice = "dirge" { c''1 } }
  \lyricsto "dirge" \new Lyrics \lyricmode { Whoops }
  \insertWhenHarmony \new Staff { a'1 }
>>

nicolas