Showing chords at changes

By default, every chord entered is printed; this behavior can be modified so that chord names are printed only at the start of lines and when the chord changes.

\version "2.24"

harmonies = \chordmode {
  c1:m c:m \break c:m c:m d
}

<<
  \new ChordNames {
    \set chordChanges = ##t
    \harmonies
  }
  \new Staff {
    \relative c' { \harmonies }
  }
>>