Automatically changing the stem direction of the middle note based on the melody

LilyPond can alter the stem direction of the middle note on a staff so that it follows the melody, by adding the Melody_engraver to the Voice context.

The context property suspendMelodyDecisions may be used to turn off this behavior locally.

\version "2.24.0"

\relative c'' {
  \time 3/4
  a8 b g f b g |
  \set suspendMelodyDecisions = ##t
  a  b g f b g |
  \unset suspendMelodyDecisions
  c  b d c b c |
}

\layout {
  \context {
    \Voice
    \consists "Melody_engraver"
    \autoBeamOff
  }
}