Re: custom replace/map of one set of pitches to another

[Valentin Petzel]

Hi Michael,

some time ago I created a function for exactly that for a stackexchange 
question:
https://music.stackexchange.com/questions/127175/lilypond-transpose-a-sequence-to-modes-with-different-intervallic-structure

Essentially it introduces a function to map one scale to another, and it does 
so by basepitch to retain alteration. One could easily adapt this function to 
match by base pitch and alteration:

transposePitchClasses =
#(define-music-function (scaleA scaleB music) (ly:music? ly:music? ly:music?)
   (let* ((scaleA (ly:music-property scaleA 'elements))
          (scaleB (ly:music-property scaleB 'elements))
          (scaleA (map (lambda (x) (ly:music-property x 'pitch)) scaleA))
          (scaleB (map (lambda (x) (ly:music-property x 'pitch)) scaleB))
          (classesA (map (lambda (p) (cons (ly:pitch-notename p) (ly:pitch-
alteration p))) scaleA)))
   (map-some-music
    (lambda (m)
      (let ((p (ly:music-property m 'pitch)))
        (if (not (null? p))
            (let* ((nn (ly:pitch-notename p))
                   (oct (ly:pitch-octave p))
                   (alt (ly:pitch-alteration p))
                   (pos (list-index (lambda (x) (and (= (car x) nn) (= (cdr x) 
alt))) classesA)))
              (if pos
                  (let* ((p2 (list-ref scaleA pos))
                         (oct2 (ly:pitch-octave p2))
                         (p3 (list-ref scaleB pos))
                         (new-pitch (ly:pitch-transpose p3 (ly:make-pitch (- 
oct oct2) 0))))
                    (ly:music-set-property! m 'pitch new-pitch)))
              m)
            #f)))
    music)
   music))

\transposePitchClasses {d fih g aih} {dih f gis a}
{ c' cis' d' dis' f' fih' fis' g' a' aih' }

Am Donnerstag, 31. August 2023, 12:53:26 CEST schrieb Michael Winter via 
LilyPond user discussion:
> I would like to do something (hopefully simple), which is basically a custom
> find and replace for a set of notes in an entire score.
> 
> For example {c cis d dis fih g aih} -> {c cis dih dis f gis a}
> 
> So basically on arbitrary list of pitches / scale  to another.
> 
> Is this possible without writing a custom function. If not, any hints on how
> to tackle the problem would be much appreciated. Thanks in advance.
> 
> -Michael

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