Grid lines: emphasizing rhythms and notes synchronization

Regular vertical lines can be drawn between staves to show note synchronization; however, in case of monophonic music, you may want to make the second stave invisible, and make the lines shorter like in this snippet.

\version "2.24"

\new ChoirStaff {
  \relative c'' <<
    \new Staff {
      \time 12/8
      \stemUp
      c4. d8 e8 f g4 f8 e8. d16 c8
    }
    \new Staff {
      % hides staff and notes so that only the grid lines are visible
      \hideNotes
      \hide Staff.BarLine
      \override Staff.StaffSymbol.line-count = #0
      \hide Staff.TimeSignature
      \hide Staff.Clef
        
      % dummy notes to force regular note spacing
      \once  \override Score.GridLine.thickness = #4.0
      c8 c c
      \once  \override Score.GridLine.thickness = #3.0
      c8 c c
      \once  \override Score.GridLine.thickness = #4.0
      c8 c c
      \once  \override Score.GridLine.thickness = #3.0
      c8 c c
    }
  >>
}

\layout {
  \context {
    \Score
    \consists "Grid_line_span_engraver"
    % center grid lines horizontally below note heads
    \override NoteColumn.X-offset = #-0.5
  }
  \context {
    \Staff
    \consists "Grid_point_engraver"
    gridInterval = #(ly:make-moment 1/8)
    % set line length and positioning:
    % two staff spaces above center line on hidden staff
    % to four spaces below center line on visible staff
    \override GridPoint.Y-extent = #'(2 . -4)
  }
}