Grid lines: changing their appearance

The appearance of grid lines can be changed by overriding some of their properties.

\version "2.24"

\new ChoirStaff <<
  \new Staff {
    \relative c'' {
      \stemUp
      c'4. d8 e8 f g4
    }
  }
  \new Staff {
    \relative c {
      % this moves them up one staff space from the default position
      \override Score.GridLine.extra-offset = #'(0.0 . 1.0)
      \stemDown
      \clef bass
      \once \override Score.GridLine.thickness = 5.0
      c4
      \once \override Score.GridLine.thickness = 1.0
      g'4
      \once \override Score.GridLine.thickness = 3.0
      f4
      \once \override Score.GridLine.thickness = 5.0
      e4
    }
  }
>>

\layout {
  \context {
    \Staff
    % set up grids
    \consists "Grid_point_engraver"
    % set the grid interval to one quarter note
    gridInterval = #(ly:make-moment 1/4)
    }
  \context {
    \Score
    \consists "Grid_line_span_engraver"
    % this moves them to the right half a staff space
    \override NoteColumn.X-offset = -0.5
  }
}