+
+ (define (analyse-synced-silence)
+ (let ((rests1 (if vs1 (rest-and-skip-events vs1) '()))
+ (rests2 (if vs2 (rest-and-skip-events vs2) '())))
+ (cond
+
+ ;; multi-measure rests (probably), which the
+ ;; part-combine iterator handles well
+ ((and (= 0 (length rests1))
+ (= 0 (length rests2)))
+ (set! (configuration now-state) 'unisilence))
+
+ ;; equal rests or equal skips, but not one of each
+ ((and (= 1 (length rests1))
+ (= 1 (length rests2))
+ (equal? (ly:event-property (car rests1) 'class)
+ (ly:event-property (car rests2) 'class))
+ (equal? (ly:event-property (car rests1) 'duration)
+ (ly:event-property (car rests2) 'duration)))
+ (set! (configuration now-state) 'unisilence))
+
+ ;; rests of different durations or mixed with
+ ;; skips or multi-measure rests
+ (else
+ ;; TODO For skips, route the rest to the shared
+ ;; voice and the skip to the voice for its part?
+ (set! (configuration now-state) 'apart-silence))
+
+ )))
+
+ (define (analyse-unsynced-silence vs1 vs2)
+ (let ((any-mmrests1 (if vs1 (any-mmrest-events vs1) #f))
+ (any-mmrests2 (if vs2 (any-mmrest-events vs2) #f)))
+ (cond
+ ;; If a multi-measure rest begins now while the other
+ ;; part has an ongoing multi-measure rest (or has
+ ;; ended), start displaying the one that begins now.
+ ((and any-mmrests1
+ (equal? (moment vs1) (moment now-state))
+ (or (not vs2) any-mmrests2))
+ (set! (configuration now-state) 'silence1))
+
+ ;; as above with parts swapped
+ ((and any-mmrests2
+ (equal? (moment vs2) (moment now-state))
+ (or (not vs1) any-mmrests1))
+ (set! (configuration now-state) 'silence2))
+ )))
+
+ (if (or vs1 vs2)
+ (let ((notes1 (if vs1 (note-events vs1) '()))
+ (notes2 (if vs2 (note-events vs2) '())))
+ ; Todo: What about a2 chords, e.g. string multi-stops?
+ ; Sort and compare notes1 and notes2?
+ (cond ((and (equal? (configuration now-state) 'chords)
+ (= 1 (length notes1))