Function get-pitches

#(define (get-pitches mus)
 (let* ((p (map
            (lambda (x) (ly:music-property x 'pitch))
            (ly:music-property mus 'elements)))
       (first-p (car p))
       (pitch (ly:pitch-notename first-p))
       (alteration (ly:pitch-alteration first-p))
       (octave -1)
       (px (ly:make-pitch octave pitch alteration)))
  (list #t p (cons px (cdr p)))))