Customizing the no-chord symbol

By default, rests in a ChordNames context cause the “N.C.” symbol to be printed. This markup can be customized.

\version "2.24.0"

<<
  \chords {
    R1
    \set noChordSymbol = "—"
    R1
    \set noChordSymbol = \markup \italic "Ssh!"
    R1
  }
  {
    R1*3
  }
>>