\version "2.18.0"

global = {
  \key g \major
  \time 6/8
  \partial 8
  % baseMoment is 1/8 by default (determined from the denominator of the time signature)
  % no need to set beatStructure either
  % beamExceptions for 6/8 are not set by default (see scm/time-signature-settings.scm)
  \set Timing.beamExceptions = #'((end . (((1 . 24) . (3 3 3 3 3 3)))))
  % the following is the same in 2.19.x syntax
  %\set Timing.beamExceptions = \beamExceptions {
  %  \scaleDurations 2/3 { \repeat unfold 6 { 16[ 16 16] } } }
}


\score {
  \new PianoStaff <<
    \new Staff = "upper"
    \relative c'' {
      \global
      %\clef treble
      \override TupletNumber #'stencil = ##f
      \override TupletBracket #'bracket-visibility = ##f
      % I’d use a markup for naming the variation.
      r8^\markup \bold { Variation 5 } |
      \tuplet 3/2 { r16 d'-3 c b bes-3 a } g8-.
      \tuplet 3/2 { r16 c-3 b a gis g-2 } fis8-. |
    }
    \new Staff = "lower"
    \relative c {
      \global
      %\clef treble
      <b''_3 d-1>8-. |
      d16 b c a b g  a g fis e d c |
      b
    }
  >>
}