#4646 Add an autoBeaming option to recognise melismata

[Simon Albrecht]

Traditionally, vocal parts have autoBeaming only inside melismata. So it would be brilliant if we had an algorithm to do this automatically and not have to add manual beams so often.
I’d suggest to make this a third option for the autoBeaming context property: #t, #f and 'melisma.

[David Kastrup]

I think this request is confused about LilyPond's default semantics. If you want "traditional" vocal beaming, you turn off autoBeaming and then use [ and ] for indicating melismata.

There is no sensible manner in which beams can indicate melismata while melismata indicate beams. So I'm voting to close this as Invalid.

[Simon Albrecht]

Correct me if I’m mistaken (and pardon my ignorance of the actual internals of this), but I can’t see the flaw.
Manual beams, i.e. BeamEvents indicate melismata. The Auto_beam_engraver however creates beams in a way that doesn’t interfere with melismata, so if he would listen (after a \set autoBeaming = #'melisma) to any events starting or ending a melisma, he could start or stop autoBeaming at these moments.
Even if a manual beam, as starting a melisma, would cause the Auto_beam_engraver to resume work: would that be a problem? If a manual beam is present, autoBeaming doesn’t interfere.

[Simon Albrecht]

I am getting your point now: you are referring to short melismata which are actually subsumed under one beam in entirety. For these, my request is obviously pointless. No, I was thinking about longer melismata, like in virtuoso baroque music, where it’s quite tedious to specify all the beams occurring in the meantime:

:::TeX
\version "2.19.28"
\language "deutsch"
\paper { #(set-paper-size "a7landscape") }
\header { tagline = ##f composer = "Seb. Bach, BWV 225" }
selfAl = \once \override LyricText . self-alignment-X = \etc
<<
  \new Voice = "sopOne" \relative {
    \set autoBeaming = ##f
    \key b \major
    \time 3/4
    r4 d''8[\melisma es16 d] c8[ d16 b]
    f'4. g16[ f] es8[ f16 g]
    f8[ es16 d] es2~
    8[ d16 c] d2~
    8[ c16 b] c2~
    8[ b16 a] b2~
    8[ a16 g] a8[ c] es4~
    8[ f16 es]\melismaEnd d8[ c] d[ b]
    g'4 r
  }
  \new Lyrics \lyricsto "sopOne" {
    Sin -- get dem \selfAl #-0.7 Herrn_…
  }
>>

That could well be left to autoBeaming.