LilyPond: Beam subdivisions lost when using compound time signatures and tuplets

Question

I'm running into this issue, hopefully user error, with both the stable (2.24.4) and development (2.25.21) branches of LilyPond. In the first measure of music, I need the beam to be subdivided every three 16th notes, but whatever numbers I try, it doesn't work. Here's the most recent thing I tried. What is the correct syntax for the current versions of LilyPond?

\version "2.24.4"
#(set-default-paper-size "legallandscape")

upperOne = \relative c' {
  \clef treble

%%%%% Time signature for first measure

  \compoundMeter #'((3 8) (3 8) (3 8))
  \accidentalStyle forget
  ees8.[( fis a~] \tuplet 5/3 { a[ aes8] } a!8.[ c] \bar "!" \break

%%%%% Time signature for second measure

  \compoundMeter #'((3 8) (3 8) (3 8) (3 16) (3 8) (3 8))

  e,[ g] bes8[ a gis] \tuplet 5/3 { g!8.[ fis8] } e8. \tuplet 5/3 { d[ e8 ] } gis4.~gis16.[ a f8.])
}

upperTwo = \relative c {
  \clef bass
  \accidentalStyle forget

%%%%% Attempt to subdivide beams - THIS is what the question is about

  \set subdivideBeams = ##t
  \set baseMoment = #(ly:make-moment 3/16)
  \set beatStructure = #'(1 1 1 1)
  \tuplet 5/3 { r16 cis([ d f e }
  \tuplet 5/3 { g f g aes bes }
  \tuplet 5/3 { b! g c d ees \clef treble }
  \tuplet 5/3 { f e! f g8 }
  \tuplet 5/3 { a!16 b c d ees }
  \tuplet 5/3 { d f e! d cis }
  \tuplet 5/3 { c! ees d c b }
  \tuplet 5/3 { bes des c bes aes] }

 %%%% Change the subdivision - this works correctly

  \set baseMoment = #(ly:make-moment 1/8)
  \tuplet 3/2 { g[ b a } \tuplet 3/2 { f e d } cis8]
  \tuplet 5/3 { \clef bass c16[ b bes a g] }
  \set subdivideBeams = ##f
  f32[ e d c b bes]
  \tuplet 5/3 { a16[ f e' g f,] }
  \set subdivideBeams = ##t

 %%%%% This also results in correct output

  \set baseMoment = #(ly:make-moment 3/16)
  \tuplet 4/3 { e[ d c' e }
  \tuplet 4/3 { c, aes' c fis,]~ }
  \tuplet 4/3 { fis[ c' ees a }
  \tuplet 4/3 { g b \clef treble g' b]) }
}


\score {
      \new PianoStaff \with { \omit TimeSignature }
  <<
    \new Staff = "upper1" \upperOne
    \new Staff = "upper2" \upperTwo
  >>
}

For anyone who's curious, this is a bit of Sorabji's First Organ Symphony, the topic of my dissertation. :)

I read the documentation and Urs Liska's article on this topic. However, it's not sticking with me. I think this feature of the software needs to be made way more intuitive, without the user having to know as much about how LilyPond handles time and how to tweak that. Most of the other features of LilyPond don't require this kind of knowledge of how to change those presets.

Answer 1

The issue here is not compound time signatures. Is that the logic for automatic subdivisions is a heuristic that depends on the time signature. In your case the time signature is 18/16, and there this heuristic just fails, as you can see with this simplified example:

{
  \time 18/16
  \set subdivideBeams = ##t
  \set baseMoment = \musicLength 8.
  \set beatStructure = #'(6)
  \tuplet 5/3 8. {
    \repeat unfold #(* 18 5/3) { 16 }
  }
}

So unless this heuristic is improved you’ll need to manually specify the subdivisions (which I think is fair, since this is quite non-trivial music.

{
  \time 18/16
  \set subdivideBeams = ##t
  \set baseMoment = \musicLength 8.
  \set beatStructure = #'(6)
  \tuplet 5/3 8. {
    \repeat unfold 5 {
      16 16 16 16 \once\set stemRightBeamCount = #1 16 \once\set stemLeftBeamCount = #1
    }
    16 16 16 16 16
  }
}

This can of course be simplified a bit:

endSD = \once\set stemRightBeamCount = #1
newSD = \once\set stemLeftBeamCount = #1

{
  \time 18/16
  \set subdivideBeams = ##t
  \set baseMoment = \musicLength 8.
  \set beatStructure = #'(6)
  \tuplet 5/3 8. {
    \repeat unfold 5 {
      16 16 16 16 \endSD 16 \newSD
    }
    16 16 16 16 16
  }
}

Note that setting these parameters is equivalent to setting Stem.beaming to the correct value (a pair of lists giving beam positions for left and right).

Answer 2

The solution was to manually force the beaming of the LH section as follows:

  \tuplet 5/3 8. { r16 cis([ d f \set stemRightBeamCount = 1 e
                \set stemLeftBeamCount = 1 g f g aes \set stemRightBeamCount = 1 bes
                \set stemLeftBeamCount = 1 b! g c d \set stemRightBeamCount = 1 ees \clef treble
                \set stemLeftBeamCount = 1 f e! f \set stemRightBeamCount = 1 g8
                \set stemLeftBeamCount = 1 a!16 b c d \set stemRightBeamCount = 1 ees
                \set stemLeftBeamCount = 1 d f e! d \set stemRightBeamCount = 1 cis
                \set stemLeftBeamCount = 1 c! ees d c \set stemRightBeamCount = 1 b
                \set stemLeftBeamCount = 1 bes des c bes aes] }

Thanks to Leo from the GNU LilyPond mailing list for making me aware this is possible.