Splitting chords

This snippet is a 2009 contribution by Gilles Thibault in lilypond-user. It splits a chord sequence into two separated voices: the first one built on the first note (usually the lowest) of every chord and the other on the remaining notes. It works well in 2.24.4 and even in 2.25.35. I find it very useful. The only drawback it doesn't work if you use «q» to repeat last chord.

\version "2.24"


 #(define (has-duration? music)
 (ly:duration? (ly:music-property music 'duration)))
 
 #(define (not-has-duration? music)
 (not (has-duration? music)))
 
 keepsOnlyFirstNote = #(define-music-function (parser location music) (ly:music?)
 (music-map
  (lambda (evt)
   (if (eq? 'EventChord (ly:music-property evt 'name))
      (let ((elts (ly:music-property evt 'elements)))
       (if (has-duration? (car elts))
            (ly:music-set-property! evt 'elements (cons
                 (car elts)
                 (filter not-has-duration? (cdr elts)))))))
  evt)
 music))
 
 deleteFirstNote = #(define-music-function (parser location music) (ly:music?)
 (music-map
  (lambda (evt)
   (if (eq? 'EventChord (ly:music-property evt 'name))
      (let ((elts (ly:music-property evt 'elements)))
           (if (has-duration? (car elts))
                (ly:music-set-property! evt 'elements  (cdr elts)))))
  evt)
 music))
 
 
 music =\relative c' {
 <c e>4-> <d f>( <b g'>) <c e>-. g2 c2
 }
 
 \markup { Music with chords }
 \new Staff \music
 \markup { Music splitted in 2 staffs }
 <<
   \new Staff \deleteFirstNote \music
   \new Staff \keepsOnlyFirstNote \music
 >>