+%
+% Totally unfold repeats, so that the non-obvious sequencing doesn't
+% confuse us. This is necessary for time stealing to work, because
+% that relies on the sequence in which we see events matching their
+% audible sequence. Also unfold multi-measure rests to equivalent
+% skips, with preceding and following bar checks, so that time stealing
+% can change the length of the pause without falling foul of the
+% implicit bar checks.
+%
+#(define (ac:unfoldMusic music)
+ (music-map
+ (lambda (m)
+ (case (ly:music-property m 'name)
+ ((UnfoldedRepeatedMusic)
+ (let
+ ((body (ly:music-property m 'element))
+ (altl (ly:music-property m 'elements))
+ (rc (ly:music-property m 'repeat-count)))
+ (if (null? altl)
+ (make-sequential-music
+ (list-tabulate rc (lambda (i) (ly:music-deep-copy body))))
+ (let ((ealtl (if (> (length altl) rc) (take altl rc) altl)))
+ (make-sequential-music
+ (apply append!
+ (append!
+ (list-tabulate
+ (- rc (length ealtl))
+ (lambda (i) (list (ly:music-deep-copy body) (ly:music-deep-copy (car ealtl)))))
+ (map (lambda (alt) (list (ly:music-deep-copy body) alt)) ealtl))))))))
+ ((EventChord)
+ (let-values
+ (((trem evl)
+ (partition (lambda (v) (eq? (ly:music-property v 'name) 'TremoloEvent))
+ (ly:music-property m 'elements))))
+ (if (null? trem)
+ m
+ (let*
+ ((tremtype (ly:music-property (car trem) 'tremolo-type))
+ (tremtype-log (1- (integer-length tremtype)))
+ (durev (find (lambda (v) (not (null? (ly:music-property v 'duration)))) evl))
+ (totaldur (if durev (ly:music-property durev 'duration) (ly:make-duration tremtype-log 0 1)))
+ (tgt-nrep (/ (duration-visual-length totaldur) (duration-log-factor tremtype-log)))
+ (eff-nrep (max (truncate tgt-nrep) 1))
+ (tremdur (ly:make-duration tremtype-log 0
+ (* (/ tgt-nrep eff-nrep) (ly:duration-scale totaldur)))))
+ (or (and (= eff-nrep tgt-nrep) (= (ash 1 tremtype-log) tremtype))
+ (ly:warning (_ "non-integer tremolo ~a:~a")
+ (duration->lily-string (duration-visual totaldur) #:force-duration #t #:time-scale 1)
+ tremtype))
+ (for-each
+ (lambda (v)
+ (or (null? (ly:music-property v 'duration))
+ (set! (ly:music-property v 'duration) tremdur)))
+ evl)
+ (set! (ly:music-property m 'elements) evl)
+ (make-sequential-music
+ (list-tabulate eff-nrep (lambda (i) (ly:music-deep-copy m))))))))
+ ((MultiMeasureRestMusic)
+ (make-sequential-music
+ (list
+ (make-music 'BarCheck)
+ (make-music 'SkipMusic 'duration (ly:music-property m 'duration))
+ (make-music 'BarCheck))))
+ (else
+ m)))
+ (unfold-repeats music)))
+