% Harm's ottavation code, lifted from 
% https://lists.gnu.org/archive/html/lilypond-user/2017-02/msg00406.html

\version "2.19.52"

%% Define new context-property 'ottavaText'

#(define (define-translator-property symbol type? description)
  (if (not (and (symbol? symbol)
                (procedure? type?)
                (string? description)))
      (ly:error "error in call of define-translator-property"))
  (if (not (equal? (object-property symbol 'translation-doc) #f))
      (ly:error (_ "symbol ~S redefined") symbol))

  (set-object-property! symbol 'translation-type? type?)
  (set-object-property! symbol 'translation-doc description)
  symbol)

#(for-each
  (lambda (x)
    (apply define-translator-property x))
    `((ottavaText
       ,list?
       "An alist of pairs with ottavation-number and markup.")))

%% Redefine 'make-ottava-set'
#(define (make-ottava-set music)
  "Set context properties for an ottava bracket."
  (let ((octavation (ly:music-property music 'ottava-number))
        (labels
          '((2 . "15ma")
            (1 . "8va")
            (0 . #f)
            (-1 . "8vb")
            (-2 . "15mb"))))

    (list (context-spec-music
           (make-apply-context
            (lambda (context)
              (let* ((offset (* -7 octavation))
                     (ctx-label-list
                       (ly:context-property context 'ottavaText))
                     (string
                       (assoc-get octavation
                                  (if (null? ctx-label-list)
                                      labels
                                      ctx-label-list))))
                (set! (ly:context-property context 'middleCOffset) offset)
                (set! (ly:context-property context 'ottavation) string)
                (ly:set-middle-C! context))))
           'Staff))))

%% Redefine 'ottava'
ottava =
#(define-music-function (octave) (integer?)
   (_i "Set the octavation.")
   (make-music 'OttavaMusic
               'elements-callback make-ottava-set
               'ottava-number octave))

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