How do I parameterize text in a re-used section of Lilypond notes?

Question

Here is a short snippet of Lilypond that I think expresses the intent of what I want to do.

verseNotes = \relative c' {
    d^\markup { \verseText } d d d16 d d8 a r4 |
    cis8 cis cis cis16 cis cis8 a r4 |
}

verseSection = \relative c' {
    \repeat volta 2 {
        \verseNotes
    }
    gis,1 |
    gis4. b8~b2 |
    \repeat volta 3 {
        verseText = "Verse (repeat 2x)"
        \verseNotes
    }
}

\relative c' {
    verseText = "Verse"
    \verseSection
}

It, of course, errors out.

I think the cause is something like verseNotes being bound at the time it is parsed, and \verseText having no value at the time. I would like to re-use the verseNotes variable, but with different values of verseText.

I’m thinking I want the “dynamic” equivalent of a function of some sort, to which I pass a text param. I see various sections in the Lilypond documentation expressing stuff in Scheme, but this is likely last thing I want to be doing while entering music.

Answer 1

Yes, you're right - you must declare the variable before using it. Hope this helps:

verseText = "Verse"

    verseNotes = \relative c' {
        d8^\markup { \verseText } d d d16 d d8 a r4 |
        cis8 cis cis cis16 cis cis8 a r4 |
    }

    verseSection = \relative c' {
        \repeat volta 2 {
            \verseNotes
        }
        gis'1 |
        gis4. b8~b2 |
    }       

    \score { 
     \new Staff \verseSection
    }

Peter's further solution, Nov 7, 2013:

verseNotes = \relative c' {
    d8 d d d16 d d8 a r4 |
    cis8 cis cis cis16 cis cis8 a r4 |
}

verseSection = \relative c' {
    \override Score.RehearsalMark #'self-alignment-X = #LEFT
    \mark \markup { \normalsize "Verse" }
    \repeat volta 2 {
        \verseNotes
    }

    gis'1 |
    gis4. b8~b2 |
    \mark \markup { \normalsize "Verse (repeat 2x)" }
    \repeat volta 3 {
        \verseNotes
    }
}

\score {
    \new Staff \verseSection
}

Answer 2

I see various sections in the Lilypond documentation expressing stuff in Scheme, but this is likely last thing I want to be doing while entering music.

Better get used to it, though. At pure LilyPond level, you can only assign static music expressions. While one can introduce a bit of variation into those using \tag, it's not really a parameterization.

You usually don't need to be "expressing stuff" while entering music and vice versa: it's quite feasible to write Scheme for schemish things (namely the parameterization) and music for musicish things by employing #{...#} judiciously.

In this case, this would look (after some tiny octave, duration, and context fixes) like:

verseNotes =
#(define-music-function (parser location verseText) (markup?)
  #{
    \relative c' {
      d8^\markup { #verseText } d d d16 d d8 a r4 |
      cis8 cis cis cis16 cis cis8 a r4 |
    }
  #})

verseSection =
#(define-music-function (parser location verseText) (markup?)
  #{
     \relative c' {
       \repeat volta 2 {
          \verseNotes #verseText
       }
       gis1 |
       gis4. b8~b2 |
       \repeat volta 3 {
          \verseNotes "Verse (repeat 2x)"
       }
     }
  #})

\relative c' {
    \new Staff \verseSection "Verse"
}

As you can see, the Scheme code compresses itself into single lines that one can learn by heart easily enough and that are only moderately infuriating.