scm/autochange.scm

   1
   2
   3 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
   4 ;; autochange - fairly related to part combining.
   5
   6 (define-public (make-autochange-music parser music)
   7   (define (generate-split-list change-moment event-list acc)
   8     (if (null? event-list)
   9         acc
  10         (let* ((now-tun (caar event-list))
  11                (evs (map car (cdar event-list)))
  12                (now (car now-tun))
  13                (notes (filter (lambda (x)
  14                                 (equal? (ly:event-property  x 'class) 'note-event))
  15                               evs))
  16                (pitch (if (pair? notes)
  17                           (ly:event-property (car notes) 'pitch)
  18                           #f)))
  19           ;; tail recursive.
  20           (if (and pitch (not (= (ly:pitch-steps pitch) 0)))
  21               (generate-split-list #f
  22                                    (cdr event-list)
  23                                    (cons (cons
  24
  25                                           (if change-moment
  26                                               change-moment
  27                                               now)
  28                                           (sign (ly:pitch-steps pitch))) acc))
  29               (generate-split-list
  30                (if pitch #f now)
  31                (cdr event-list) acc)))))
  32
  33   (let* ((m (make-music 'AutoChangeMusic))
  34         (m1 (make-non-relative-music (context-spec-music music 'Voice "one")))
  35          (context-list (recording-group-emulate music
  36                                                 (ly:parser-lookup parser 'partCombineListener)))
  37          (evs (car context-list))
  38          (rev (reverse! (cdar context-list)))
  39          (split (reverse! (generate-split-list
  40                            #f
  41                            rev
  42                            '())
  43                           '())))
  44     (set! (ly:music-property m 'element) music)
  45     (set! (ly:music-property m 'split-list) split)
  46     m))