\version "2.22.0"

tuneMIDI =
#(define-music-function (scale music) (list? ly:music?)
   (for-some-music
     (lambda (m)
       (let ((pitch (ly:music-property m 'pitch)))
         (if (ly:pitch? pitch)
             (let* ((tones (ly:pitch-tones pitch))
                    (r (ly:moment-main
                         (ly:moment-mod
                           (ly:make-moment tones 0)
                           (ly:make-moment 6 0))))
                    (offset (assv-ref scale r)))
               (ly:message "~s" r)
               (if offset
                   (let* ((transpose-pitch (ly:make-pitch 0 0 offset))
                          (new-pitch (ly:pitch-transpose pitch transpose-pitch)))
                     (ly:music-set-property! m 'pitch new-pitch)
                     #t)
                   #f))
             #f)))
     music)
   music)

myNotes = \relative { a b c d e f gis a b c d e f gis a }

{ \myNotes }

\score {
  \tuneMIDI
    #'(
       ; Lower F (5/2 tones above C) by 1/10 tone.
       (5/2 . -1/10)
       ; Raise G# by 1/10 tone.
       (4 . 1/10)
       )
    \myNotes
  \midi { }
}