Normalized \transposition

The \transposition command allows to typeset transposing parts. However, when multiple transposing instruments are used, one may want to normalize these transpositions to print the score in one single key. Here is how to achieve it.

\version "2.24.0"

%% http://lsr.di.unimi.it/LSR/Item?id=697
%% see also http://lilypond.1069038.n5.nabble.com/LSR-v2-18-quot-Normalized-transposition-quot-does-not-compile-tc159368.html

%LSR contributed by Jay Anderson http://lists.gnu.org/archive/html/lilypond-user/2008-06/msg00426.html
%% see upraded version by David Kastrup on Feb. 15, 2014.
%% "it might be worth just using quoted music for that: it automatically transforms itself into concert pitch."

#(define (adjust-note mus key currkey)
 (cond ((eq? (ly:music-property mus 'name) 'NoteEvent)
         (ly:music-transpose mus (car currkey)))
       ((and
          (eq? (ly:music-property mus 'name) 'PropertySet)
          (eq? (ly:music-property mus 'symbol) 'instrumentTransposition))
         (set-car! currkey (ly:music-property mus 'value))
         (ly:music-set-property! mus 'value (ly:make-pitch 0 0 0))
         mus)
       (else mus)))

normalizeTransposition =
#(define-music-function (key music) (ly:pitch? ly:music?)
 (ly:music-transpose
   (let ((currkey (list (ly:make-pitch 0 0 0))))
     (music-map (lambda (x) (adjust-note x key currkey)) music))
   (ly:pitch-negate key)))

music = \relative c' {
 \time 4/4
 \transposition f
 c e g c |
 \transposition ees
 c, e g c |
 \transposition d
 c, e g c |
}

\score {
 <<
   \new Staff {
     \music
   }
   \new Staff {
     \normalizeTransposition f \music
   }
 >>
 \layout {}
 \midi {}
}