X-Git-Url: https://git.donarmstrong.com/?a=blobdiff_plain;f=scm%2Fpart-combiner.scm;h=94860cdf6fc5a56103e700abab7a6140a0d1f02a;hb=HEAD;hp=88c0b88fa6be7d94d61f6d8f40c946176c449309;hpb=f7ee0ca6ef6650af9b091782cb03375be6d890f8;p=lilypond.git

diff --git a/scm/part-combiner.scm b/scm/part-combiner.scm
index 88c0b88fa6..94860cdf6f 100644
--- a/scm/part-combiner.scm
+++ b/scm/part-combiner.scm
@@ -1,6 +1,6 @@
 ;;;; This file is part of LilyPond, the GNU music typesetter.
 ;;;;
-;;;; Copyright (C) 2004--2012 Han-Wen Nienhuys <hanwen@xs4all.nl>
+;;;; Copyright (C) 2004--2015 Han-Wen Nienhuys <hanwen@xs4all.nl>
 ;;;;
 ;;;; LilyPond is free software: you can redistribute it and/or modify
 ;;;; it under the terms of the GNU General Public License as published by
@@ -20,7 +20,7 @@
 
 (define-class <Voice-state> ()
   (event-list #:init-value '() #:accessor events #:init-keyword #:events)
-  (when-moment #:accessor when #:init-keyword #:when)
+  (when-moment #:accessor moment #:init-keyword #:moment)
   (tuning #:accessor tuning #:init-keyword #:tuning)
   (split-index #:accessor split-index)
   (vector-index)
@@ -32,24 +32,73 @@
   (spanner-state #:init-value '() #:accessor span-state))
 
 (define-method (write (x <Voice-state> ) file)
-  (display (when x) file)
+  (display (moment x) file)
   (display " evs = " file)
   (display (events x) file)
   (display " active = " file)
   (display (span-state x) file)
   (display "\n" file))
 
+;; Return the duration of the longest event in the Voice-state.
+(define-method (duration (vs <Voice-state>))
+  (define (duration-max event d1)
+    (let ((d2 (ly:event-property event 'duration #f)))
+      (if d2
+          (if (ly:duration<? d1 d2) d2 d1)
+          d1)))
+
+  (fold duration-max (ly:make-duration 0 0 0) (events vs)))
+
+;; Return the moment that the longest event in the Voice-state ends.
+(define-method (end-moment (vs <Voice-state>))
+  (ly:moment-add (moment vs) (ly:duration-length (duration vs))))
+
 (define-method (note-events (vs <Voice-state>))
   (define (f? x)
-    (equal? (ly:event-property	x 'class) 'note-event))
+    (ly:in-event-class? x 'note-event))
   (filter f? (events vs)))
 
+; Return a list of note events which is sorted and stripped of
+; properties that we do not want to prevent combining parts.
+(define-method (comparable-note-events (vs <Voice-state>))
+  (define (note<? note1 note2)
+    (let ((p1 (ly:event-property note1 'pitch))
+          (p2 (ly:event-property note2 'pitch)))
+      (cond ((ly:pitch<? p1 p2) #t)
+            ((ly:pitch<? p2 p1) #f)
+            (else (ly:duration<? (ly:event-property note1 'duration)
+                                 (ly:event-property note2 'duration))))))
+  ;; TODO we probably should compare articulations too
+  (sort (map (lambda (x)
+               (ly:make-stream-event
+                (ly:make-event-class 'note-event)
+                (list (cons 'duration (ly:event-property x 'duration))
+                      (cons 'pitch (ly:event-property x 'pitch)))))
+             (note-events vs))
+        note<?))
+
+(define-method (rest-or-skip-events (vs <Voice-state>))
+  (define (filtered-events event-class)
+    (filter (lambda(x) (ly:in-event-class? x event-class))
+            (events vs)))
+  (let ((result (filtered-events 'rest-event)))
+    ;; There may be skips in the same part with rests for various
+    ;; reasons.  Regard the skips only if there are no rests.
+    (if (and (not (pair? result)) (not (any-mmrest-events vs)))
+        (set! result (filtered-events 'skip-event)))
+  result))
+
+(define-method (any-mmrest-events (vs <Voice-state>))
+  (define (f? x)
+    (ly:in-event-class? x 'multi-measure-rest-event))
+  (any f? (events vs)))
+
 (define-method (previous-voice-state (vs <Voice-state>))
   (let ((i (slot-ref vs 'vector-index))
-	(v (slot-ref vs 'state-vector)))
+        (v (slot-ref vs 'state-vector)))
     (if (< 0 i)
-	(vector-ref v (1- i))
-	#f)))
+        (vector-ref v (1- i))
+        #f)))
 
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
@@ -58,21 +107,34 @@
   (configuration #:init-value '() #:accessor configuration)
   ;; Allow overriding split configuration, takes precedence over configuration
   (forced-configuration #:init-value #f #:accessor forced-configuration)
-  (when-moment #:accessor when #:init-keyword #:when)
+  (when-moment #:accessor moment #:init-keyword #:moment)
   ;; voice-states are states starting with the Split-state or later
   ;;
   (is #:init-keyword #:voice-states #:accessor voice-states)
-  (synced  #:init-keyword #:synced #:init-value	 #f #:getter synced?))
+  (synced  #:init-keyword #:synced #:init-value  #f #:getter synced?))
 
 
 (define-method (write (x <Split-state> ) f)
-  (display (when x) f)
+  (display (moment x) f)
   (display " = " f)
   (display (configuration x) f)
   (if (synced? x)
       (display " synced "))
   (display "\n" f))
 
+(define-method (current-or-previous-voice-states (ss <Split-state>))
+  "Return voice states meeting the following conditions.  For a voice
+in sync, return the current voice state.  For a voice out of sync,
+return the previous voice state."
+  (let* ((vss (voice-states ss))
+         (vs1 (car vss))
+         (vs2 (cdr vss)))
+    (if (and vs1 (not (equal? (moment vs1) (moment ss))))
+        (set! vs1 (previous-voice-state vs1)))
+    (if (and vs2 (not (equal? (moment vs2) (moment ss))))
+        (set! vs2 (previous-voice-state vs2)))
+    (cons vs1 vs2)))
+
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
 
@@ -81,16 +143,32 @@
     (if p (span-state p) '())))
 
 (define (make-voice-states evl)
-  (let ((vec (list->vector (map (lambda (v)
-				  (make <Voice-state>
-				    #:when (caar v)
-				    #:tuning (cdar v)
-				    #:events (map car (cdr v))))
-				evl))))
-    (do ((i 0 (1+ i)))
-	((= i (vector-length vec)) vec)
-      (slot-set! (vector-ref vec i) 'vector-index i)
-      (slot-set! (vector-ref vec i) 'state-vector vec))))
+  (let* ((states (map (lambda (v)
+                        (make <Voice-state>
+                          #:moment (caar v)
+                          #:tuning (cdar v)
+                          #:events (map car (cdr v))))
+                      (reverse evl))))
+
+    ;; add an entry with no events at the moment the last event ends
+    (if (pair? states)
+        (let ((last-real-event (car states)))
+          (set! states
+                (cons (make <Voice-state>
+                        #:moment (end-moment last-real-event)
+                        #:tuning (tuning last-real-event)
+                        #:events '())
+                      states))))
+
+    ;; TODO: Add an entry at +inf.0 and see if it allows us to remove
+    ;; the many instances of conditional code handling the case that
+    ;; there is no voice state at a given moment.
+
+    (let ((vec (list->vector (reverse! states))))
+      (do ((i 0 (1+ i)))
+          ((= i (vector-length vec)) vec)
+        (slot-set! (vector-ref vec i) 'vector-index i)
+        (slot-set! (vector-ref vec i) 'state-vector vec)))))
 
 (define (make-split-state vs1 vs2)
   "Merge lists VS1 and VS2, containing Voice-state objects into vector
@@ -99,29 +177,29 @@ Voice-state objects
 "
   (define (helper ss-idx ss-list idx1 idx2)
     (let* ((state1 (if (< idx1 (vector-length vs1)) (vector-ref vs1 idx1) #f))
-	   (state2 (if (< idx2 (vector-length vs2)) (vector-ref vs2 idx2) #f))
-	   (min (cond ((and state1 state2) (moment-min (when state1) (when state2)))
-		      (state1 (when state1))
-		      (state2 (when state2))
-		      (else #f)))
-	   (inc1 (if (and state1 (equal? min (when state1))) 1 0))
-	   (inc2 (if (and state2 (equal? min (when state2))) 1 0))
-	   (ss-object (if min
-			  (make <Split-state>
-			    #:when min
-			    #:voice-states (cons state1 state2)
-			    #:synced (= inc1 inc2))
-			  #f)))
+           (state2 (if (< idx2 (vector-length vs2)) (vector-ref vs2 idx2) #f))
+           (min (cond ((and state1 state2) (moment-min (moment state1) (moment state2)))
+                      (state1 (moment state1))
+                      (state2 (moment state2))
+                      (else #f)))
+           (inc1 (if (and state1 (equal? min (moment state1))) 1 0))
+           (inc2 (if (and state2 (equal? min (moment state2))) 1 0))
+           (ss-object (if min
+                          (make <Split-state>
+                            #:moment min
+                            #:voice-states (cons state1 state2)
+                            #:synced (= inc1 inc2))
+                          #f)))
       (if state1
-	  (set! (split-index state1) ss-idx))
+          (set! (split-index state1) ss-idx))
       (if state2
-	  (set! (split-index state2) ss-idx))
+          (set! (split-index state2) ss-idx))
       (if min
-	  (helper (1+ ss-idx)
-		  (cons ss-object ss-list)
-		  (+ idx1 inc1)
-		  (+ idx2 inc2))
-	  ss-list)))
+          (helper (1+ ss-idx)
+                  (cons ss-object ss-list)
+                  (+ idx1 inc1)
+                  (+ idx2 inc2))
+          ss-list)))
   (list->vector (reverse! (helper 0 '() 0  0) '())))
 
 (define (analyse-spanner-states voice-state-vec)
@@ -130,143 +208,135 @@ Voice-state objects
     "Analyse EVS at INDEX, given state ACTIVE."
 
     (define (analyse-tie-start active ev)
-      (if (equal? (ly:event-property ev 'class) 'tie-event)
-	  (acons 'tie (split-index (vector-ref voice-state-vec index))
-		 active)
-	  active))
+      (if (ly:in-event-class? ev 'tie-event)
+          (acons 'tie (split-index (vector-ref voice-state-vec index))
+                 active)
+          active))
 
     (define (analyse-tie-end active ev)
-      (if (equal? (ly:event-property ev 'class) 'note-event)
-	  (assoc-remove! active 'tie)
-	  active))
+      (if (ly:in-event-class? ev 'note-event)
+          (assoc-remove! active 'tie)
+          active))
 
     (define (analyse-absdyn-end active ev)
-      (if (or (equal? (ly:event-property ev 'class) 'absolute-dynamic-event)
-	      (and (equal? (ly:event-property ev 'class) 'crescendo-event)
-		   (equal? STOP (ly:event-property ev 'span-direction))))
-	  (assoc-remove! (assoc-remove! active 'cresc) 'decr)
-	  active))
+      (if (or (ly:in-event-class? ev 'absolute-dynamic-event)
+              (and (ly:in-event-class? ev 'span-dynamic-event)
+                   (equal? STOP (ly:event-property ev 'span-direction))))
+          (assoc-remove! (assoc-remove! active 'cresc) 'decr)
+          active))
 
     (define (active<? a b)
       (cond ((symbol<? (car a) (car b)) #t)
-	    ((symbol<? (car b) (car a)) #f)
-	    (else (< (cdr a) (cdr b)))))
+            ((symbol<? (car b) (car a)) #f)
+            (else (< (cdr a) (cdr b)))))
 
     (define (analyse-span-event active ev)
-      (let* ((name (ly:event-property ev 'class))
-	     (key (cond ((equal? name 'slur-event) 'slur)
-			((equal? name 'phrasing-slur-event) 'tie)
-			((equal? name 'beam-event) 'beam)
-			((equal? name 'crescendo-event) 'cresc)
-			((equal? name 'decrescendo-event) 'decr)
-			(else #f)))
-	     (sp (ly:event-property ev 'span-direction)))
-	(if (and (symbol? key) (ly:dir? sp))
-	    (if (= sp STOP)
-		(assoc-remove! active key)
-		(acons key
-		       (split-index (vector-ref voice-state-vec index))
-		       active))
-	    active)))
+      (let* ((name (car (ly:event-property ev 'class)))
+             (key (cond ((equal? name 'slur-event) 'slur)
+                        ((equal? name 'phrasing-slur-event) 'tie)
+                        ((equal? name 'beam-event) 'beam)
+                        ((equal? name 'crescendo-event) 'cresc)
+                        ((equal? name 'decrescendo-event) 'decr)
+                        (else #f)))
+             (sp (ly:event-property ev 'span-direction)))
+        (if (and (symbol? key) (ly:dir? sp))
+            (if (= sp STOP)
+                (assoc-remove! active key)
+                (acons key
+                       (split-index (vector-ref voice-state-vec index))
+                       active))
+            active)))
 
     (define (analyse-events active evs)
       "Run all analyzers on ACTIVE and EVS"
       (define (run-analyzer analyzer active evs)
-	(if (pair? evs)
-	    (run-analyzer analyzer (analyzer active (car evs)) (cdr evs))
-	    active))
+        (if (pair? evs)
+            (run-analyzer analyzer (analyzer active (car evs)) (cdr evs))
+            active))
       (define (run-analyzers analyzers active evs)
-	(if (pair? analyzers)
-	    (run-analyzers (cdr analyzers)
-			   (run-analyzer (car analyzers) active evs)
-			   evs)
-	    active))
+        (if (pair? analyzers)
+            (run-analyzers (cdr analyzers)
+                           (run-analyzer (car analyzers) active evs)
+                           evs)
+            active))
       (sort ;; todo: use fold or somesuch.
        (run-analyzers (list analyse-absdyn-end analyse-span-event
-			    ;; note: tie-start/span comes after tie-end/absdyn.
-			    analyse-tie-end analyse-tie-start)
-		      active evs)
+                            ;; note: tie-start/span comes after tie-end/absdyn.
+                            analyse-tie-end analyse-tie-start)
+                      active evs)
        active<?))
 
     ;; must copy, since we use assoc-remove!
     (if (< index (vector-length voice-state-vec))
-	(begin
-	  (set! active (analyse-events active (events (vector-ref voice-state-vec index))))
-	  (set! (span-state (vector-ref voice-state-vec index))
-		(list-copy active))
-	  (helper (1+ index) active))))
+        (begin
+          (set! active (analyse-events active (events (vector-ref voice-state-vec index))))
+          (set! (span-state (vector-ref voice-state-vec index))
+                (list-copy active))
+          (helper (1+ index) active))))
 
   (helper 0 '()))
 
+(define recording-group-functions
+  ;;Selected parts from @var{toplevel-music-functions} not requiring @code{parser}.
+  (list
+   (lambda (music) (expand-repeat-chords! '(rhythmic-event) music))
+   expand-repeat-notes!))
+
+
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 (define-public (recording-group-emulate music odef)
   "Interpret @var{music} according to @var{odef}, but store all events
 in a chronological list, similar to the @code{Recording_group_engraver} in
 LilyPond version 2.8 and earlier."
   (let*
-     ((context-list '())
-      (now-mom (ly:make-moment 0 0))
-      (global (ly:make-global-context odef))
-      (mom-listener (ly:make-listener
-             (lambda (tev) (set! now-mom (ly:event-property tev 'moment)))))
-      (new-context-listener
-       (ly:make-listener
+      ((context-list '())
+       (now-mom (ly:make-moment 0 0))
+       (global (ly:make-global-context odef))
+       (mom-listener (lambda (tev) (set! now-mom (ly:event-property tev 'moment))))
+       (new-context-listener
         (lambda (sev)
           (let*
-             ((child (ly:event-property sev 'context))
-              (this-moment-list (cons (ly:context-id child) '()))
-              (dummy (set! context-list (cons this-moment-list context-list)))
-              (acc '())
-              (accumulate-event-listener
-                  (ly:make-listener (lambda (ev)
-                                       (set! acc (cons (cons ev #t) acc)))))
-              (save-acc-listener
-                  (ly:make-listener (lambda (tev)
-                      (if (pair? acc)
-                        (let ((this-moment
-                              (cons (cons now-mom
-                                (ly:context-property child 'instrumentTransposition))
-                                ;; The accumulate-event-listener above creates
-                                ;; the list of events in reverse order, so we
-                                ;; have to revert it to the original order again
-                                (reverse acc))))
-                          (set-cdr! this-moment-list
-                                (cons this-moment (cdr this-moment-list)))
-                          (set! acc '())))))))
+              ((child (ly:event-property sev 'context))
+               (this-moment-list (cons (ly:context-id child) '()))
+               (dummy (set! context-list (cons this-moment-list context-list)))
+               (acc '())
+               (accumulate-event-listener
+                (lambda (ev)
+                  (set! acc (cons (cons ev #t) acc))))
+               (save-acc-listener
+                (lambda (tev)
+                  (if (pair? acc)
+                      (let ((this-moment
+                             (cons (cons now-mom
+                                         (ly:context-property child 'instrumentTransposition))
+                                   ;; The accumulate-event-listener above creates
+                                   ;; the list of events in reverse order, so we
+                                   ;; have to revert it to the original order again
+                                   (reverse acc))))
+                        (set-cdr! this-moment-list
+                                  (cons this-moment (cdr this-moment-list)))
+                        (set! acc '()))))))
             (ly:add-listener accumulate-event-listener
-                (ly:context-event-source child) 'StreamEvent)
+                             (ly:context-event-source child) 'StreamEvent)
             (ly:add-listener save-acc-listener
-                (ly:context-event-source global) 'OneTimeStep))))))
+                             (ly:context-event-source global) 'OneTimeStep)))))
     (ly:add-listener new-context-listener
-        (ly:context-events-below global) 'AnnounceNewContext)
+                     (ly:context-events-below global) 'AnnounceNewContext)
     (ly:add-listener mom-listener (ly:context-event-source global) 'Prepare)
-    (ly:interpret-music-expression (make-non-relative-music music) global)
+    (ly:interpret-music-expression
+     (make-non-relative-music
+      (fold (lambda (x m) (x m)) music recording-group-functions))
+     global)
     context-list))
 
-(define-public (make-part-combine-music parser music-list direction)
-  (let* ((m (make-music 'PartCombineMusic))
-	 (m1 (make-non-relative-music (context-spec-music (first music-list) 'Voice "one")))
-	 (m2  (make-non-relative-music  (context-spec-music (second music-list) 'Voice "two")))
-	 (listener (ly:parser-lookup parser 'partCombineListener))
-	 (evs2 (recording-group-emulate m2 listener))
-	 (evs1 (recording-group-emulate m1 listener)))
-
-    (set! (ly:music-property m 'elements) (list m1 m2))
-    (set! (ly:music-property m 'direction) direction)
-    (set! (ly:music-property m 'split-list)
-	  (if (and (assoc "one" evs1) (assoc "two" evs2))
-	      (determine-split-list (reverse! (assoc-get "one" evs1) '())
-				    (reverse! (assoc-get "two" evs2) '()))
-	      '()))
-    m))
-
-(define-public (determine-split-list evl1 evl2)
-  "@var{evl1} and @var{evl2} should be ascending."
+(define-public (determine-split-list evl1 evl2 chord-range)
+  "@var{evl1} and @var{evl2} should be ascending. @var{chord-range} is a pair of numbers (min . max) defining the distance in steps between notes that may be combined into a chord or unison."
   (let* ((pc-debug #f)
-	 (chord-threshold 8)
-	 (voice-state-vec1 (make-voice-states evl1))
-	 (voice-state-vec2 (make-voice-states evl2))
-	 (result (make-split-state voice-state-vec1 voice-state-vec2)))
+         (voice-state-vec1 (make-voice-states evl1))
+         (voice-state-vec2 (make-voice-states evl2))
+         (result (make-split-state voice-state-vec1 voice-state-vec2))
+         (chord-min-diff (car chord-range))
+         (chord-max-diff (cdr chord-range)))
 
     ;; Go through all moments recursively and check if the events of that
     ;; moment contain a part-combine-force-event override. If so, store its
@@ -275,274 +345,391 @@ LilyPond version 2.8 and earlier."
     (define (analyse-forced-combine result-idx prev-res)
 
       (define (get-forced-event x)
-	(if (ly:in-event-class? x 'part-combine-force-event)
-	    (cons (ly:event-property x 'forced-type) (ly:event-property x 'once))
-	    #f))
+        (cond
+         ((and (ly:in-event-class? x 'SetProperty)
+               (eq? (ly:event-property x 'symbol) 'partCombineForced))
+          (cons (ly:event-property x 'value #f)
+                (ly:event-property x 'once #f)))
+         ((and (ly:in-event-class? x 'UnsetProperty)
+               (eq? (ly:event-property x 'symbol) 'partCombineForced))
+          (cons #f (ly:event-property x 'once #f)))
+         (else #f)))
+
       (define (part-combine-events vs)
-	(if (not vs)
-	    '()
-	    (filter-map get-forced-event (events vs))))
+        (if (not vs)
+            '()
+            (filter-map get-forced-event (events vs))))
       ;; end part-combine-events
 
       ;; forced-result: Take the previous config and analyse whether
       ;; any change happened.... Return new once and permanent config
       (define (forced-result evt state)
-	;; sanity check, evt should always be (new-state . once)
-	(if (not (and (pair? evt) (pair? state)))
-	    state
-	    (if (cdr evt)
-		;; Once-event, leave permanent state unchanged
-		(cons (car evt) (cdr state))
-		;; permanent change, leave once state unchanged
-		(cons (car state) (car evt)))))
+        ;; sanity check, evt should always be (new-state . once)
+        (if (not (and (pair? evt) (pair? state)))
+            state
+            (if (cdr evt)
+                ;; Once-event, leave permanent state unchanged
+                (cons (car evt) (cdr state))
+                ;; permanent change, leave once state unchanged
+                (cons (car state) (car evt)))))
       ;; end forced-combine-result
 
       ;; body of analyse-forced-combine:
       (if (< result-idx (vector-length result))
-	  (let* ((now-state (vector-ref result result-idx)) ; current result
-		 ;; Extract all part-combine force events
-		 (ev1 (part-combine-events (car (voice-states now-state))))
-		 (ev2 (part-combine-events (cdr (voice-states now-state))))
-		 (evts (append ev1 ev2))
-		 ;; result is (once-state permament-state):
-		 (state (fold forced-result (cons 'automatic prev-res) evts))
-		 ;; Now let once override permanent changes:
-		 (force-state (if (equal? (car state) 'automatic)
-				  (cdr state)
-				  (car state))))
-	    (set! (forced-configuration (vector-ref result result-idx))
-		  force-state)
-	    ;; For the next moment, ignore the once override (car stat)
-	    ;; and pass on the permanent override, stored as (cdr state)
-	    (analyse-forced-combine (1+ result-idx) (cdr state)))))
+          (let* ((now-state (vector-ref result result-idx)) ; current result
+                 ;; Extract all part-combine force events
+                 (evts (if (synced? now-state)
+                           (append
+                            (part-combine-events (car (voice-states now-state)))
+                            (part-combine-events (cdr (voice-states now-state))))
+                           '()))
+                 ;; result is (once-state permament-state):
+                 (state (fold forced-result (cons 'automatic prev-res) evts))
+                 ;; Now let once override permanent changes:
+                 (force-state (if (equal? (car state) 'automatic)
+                                  (cdr state)
+                                  (car state))))
+            (set! (forced-configuration (vector-ref result result-idx))
+                  force-state)
+            ;; For the next moment, ignore the once override (car stat)
+            ;; and pass on the permanent override, stored as (cdr state)
+            (analyse-forced-combine (1+ result-idx) (cdr state)))))
     ;; end analyse-forced-combine
 
 
     (define (analyse-time-step result-idx)
       (define (put x . index)
-	"Put the result to X, starting from INDEX backwards.
+        "Put the result to X, starting from INDEX backwards.
 
 Only set if not set previously.
 "
-	(let ((i (if (pair? index) (car index) result-idx)))
-	  (if (and (<= 0 i)
-		   (not (symbol? (configuration (vector-ref result i)))))
-	      (begin
-		(set! (configuration (vector-ref result i)) x)
-		(put x (1- i))))))
+        (let ((i (if (pair? index) (car index) result-idx)))
+          (if (and (<= 0 i)
+                   (not (symbol? (configuration (vector-ref result i)))))
+              (begin
+                (set! (configuration (vector-ref result i)) x)
+                (put x (1- i))))))
 
       (define (copy-state-from state-vec vs)
-	(define (copy-one-state key-idx)
-	  (let* ((idx (cdr key-idx))
-		 (prev-ss (vector-ref result idx))
-		 (prev (configuration prev-ss)))
-	    (if (symbol? prev)
-		(put prev))))
-	(map copy-one-state (span-state vs)))
+        (define (copy-one-state key-idx)
+          (let* ((idx (cdr key-idx))
+                 (prev-ss (vector-ref result idx))
+                 (prev (configuration prev-ss)))
+            (if (symbol? prev)
+                (put prev))))
+        (for-each copy-one-state (span-state vs)))
 
       (define (analyse-notes now-state)
-	(let* ((vs1 (car (voice-states now-state)))
-	       (vs2 (cdr (voice-states now-state)))
-	       (notes1 (note-events vs1))
-	       (durs1 (sort (map (lambda (x) (ly:event-property x 'duration))
-				 notes1)
-			    ly:duration<?))
-	       (pitches1 (sort (map (lambda (x) (ly:event-property x 'pitch))
-				    notes1)
-			       ly:pitch<?))
-	       (notes2 (note-events vs2))
-	       (durs2 (sort (map (lambda (x) (ly:event-property x 'duration))
-				 notes2)
-			    ly:duration<?))
-	       (pitches2 (sort (map (lambda (x) (ly:event-property x 'pitch))
-				    notes2)
-			       ly:pitch<?)))
-	  (cond ((> (length notes1) 1) (put 'apart))
-		((> (length notes2) 1) (put 'apart))
-		((= 1 (+ (length notes2) (length notes1))) (put 'apart))
-		((and (= (length durs1) 1)
-		      (= (length durs2) 1)
-		      (not (equal? (car durs1) (car durs2))))
-		 (put 'apart))
-		(else
-		 (if (and (= (length pitches1) (length pitches2)))
-		     (if (and (pair? pitches1)
-			      (pair? pitches2)
-			      (or
-			       (< chord-threshold (ly:pitch-steps
-						   (ly:pitch-diff (car pitches1)
-								  (car pitches2))))
-
-			       ;; voice crossings:
-			       (> 0 (ly:pitch-steps (ly:pitch-diff (car pitches1)
-								   (car pitches2))))
-			       ))
-			 (put 'apart)
-			 ;; copy previous split state from spanner state
-			 (begin
-			   (if (previous-voice-state vs1)
-			       (copy-state-from voice-state-vec1
-						(previous-voice-state vs1)))
-			   (if (previous-voice-state vs2)
-			       (copy-state-from voice-state-vec2
-						(previous-voice-state vs2)))
-			   (if (and (null? (span-state vs1)) (null? (span-state vs2)))
-			       (put 'chords)))))))))
+        (let* ((vs1 (car (voice-states now-state)))
+               (vs2 (cdr (voice-states now-state)))
+               (notes1 (comparable-note-events vs1))
+               (notes2 (comparable-note-events vs2)))
+          (cond
+           ;; if neither part has notes, do nothing
+           ((and (not (pair? notes1)) (not (pair? notes2))))
+
+           ;; if one part has notes and the other does not
+           ((or (not (pair? notes1)) (not (pair? notes2))) (put 'apart))
+
+           ;; if either part has a chord
+           ((or (> (length notes1) 1) 
+                (> (length notes2) 1))
+            (if (and (<= chord-min-diff 0) ; user requests combined unisons
+                     (equal? notes1 notes2)) ; both parts have the same chord
+                (put 'chords)
+                (put 'apart)))
+
+           ;; if the durations are different
+           ;; TODO articulations too?
+           ((and (not (equal? (ly:event-property (car notes1) 'duration)
+                              (ly:event-property (car notes2) 'duration))))
+            (put 'apart))
+
+           (else
+            ;; Is the interval outside of chord-range?
+            (if (let ((diff (ly:pitch-steps
+                             (ly:pitch-diff 
+                              (ly:event-property (car notes1) 'pitch)
+                              (ly:event-property (car notes2) 'pitch)))))
+                  (or (< diff chord-min-diff)
+                      (> diff chord-max-diff)
+                      ))
+                (put 'apart)
+                ;; copy previous split state from spanner state
+                (begin
+                  (if (previous-voice-state vs1)
+                      (copy-state-from voice-state-vec1
+                                       (previous-voice-state vs1)))
+                  (if (previous-voice-state vs2)
+                      (copy-state-from voice-state-vec2
+                                       (previous-voice-state vs2)))
+                  (if (and (null? (span-state vs1)) (null? (span-state vs2)))
+                      (put 'chords))))))))
 
       (if (< result-idx (vector-length result))
-	  (let* ((now-state (vector-ref result result-idx))
-		 (vs1 (car (voice-states now-state)))
-		 (vs2 (cdr (voice-states now-state))))
-
-	    (cond ((not vs1) (put 'apart))
-		  ((not vs2) (put 'apart))
-		  (else
-		   (let ((active1 (previous-span-state vs1))
-			 (active2 (previous-span-state vs2))
-			 (new-active1 (span-state vs1))
-			 (new-active2 (span-state vs2)))
-		     (if #f ; debug
-			 (display (list (when now-state) result-idx
-					active1 "->" new-active1
-					active2 "->" new-active2
-					"\n")))
-		     (if (and (synced? now-state)
-			      (equal? active1 active2)
-			      (equal? new-active1 new-active2))
-			 (analyse-notes now-state)
-
-			 ;; active states different:
-			 (put 'apart)))
-
-		   ;; go to the next one, if it exists.
-		   (analyse-time-step (1+ result-idx)))))))
+          (let* ((now-state (vector-ref result result-idx))
+                 (vs1 (car (voice-states now-state)))
+                 (vs2 (cdr (voice-states now-state))))
+
+            (cond ((not vs1) (put 'apart))
+                  ((not vs2) (put 'apart))
+                  (else
+                   (let ((active1 (previous-span-state vs1))
+                         (active2 (previous-span-state vs2))
+                         (new-active1 (span-state vs1))
+                         (new-active2 (span-state vs2)))
+                     (if #f ; debug
+                         (display (list (moment now-state) result-idx
+                                        active1 "->" new-active1
+                                        active2 "->" new-active2
+                                        "\n")))
+                     (if (and (synced? now-state)
+                              (equal? active1 active2)
+                              (equal? new-active1 new-active2))
+                         (analyse-notes now-state)
+
+                         ;; active states different:
+                         (put 'apart)))
+
+                   ;; go to the next one, if it exists.
+                   (analyse-time-step (1+ result-idx)))))))
 
     (define (analyse-a2 result-idx)
       (if (< result-idx (vector-length result))
-	  (let* ((now-state (vector-ref result result-idx))
-		 (vs1 (car (voice-states now-state)))
-		 (vs2 (cdr (voice-states now-state))))
-	    (if (and (equal? (configuration now-state) 'chords)
-		     vs1 vs2)
-		(let ((notes1 (note-events vs1))
-		      (notes2 (note-events vs2)))
-		  (cond ((and (= 1 (length notes1))
-			      (= 1 (length notes2))
-			      (equal? (ly:event-property (car notes1) 'pitch)
-				      (ly:event-property (car notes2) 'pitch)))
-			 (set! (configuration now-state) 'unisono))
-			((and (= 0 (length notes1))
-			      (= 0 (length notes2)))
-			 (set! (configuration now-state) 'unisilence)))))
-	    (analyse-a2 (1+ result-idx)))))
+          (let* ((now-state (vector-ref result result-idx))
+                 (vs1 (car (voice-states now-state)))
+                 (vs2 (cdr (voice-states now-state))))
+
+            (define (analyse-synced-silence)
+              (let ((rests1 (if vs1 (rest-or-skip-events vs1) '()))
+                    (rests2 (if vs2 (rest-or-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 (comparable-note-events vs1) '()))
+                      (notes2 (if vs2 (comparable-note-events vs2) '())))
+                  (cond ((and (equal? (configuration now-state) 'chords)
+                              (pair? notes1)
+                              (equal? notes1 notes2))
+                         (set! (configuration now-state) 'unisono))
+
+                        ((synced? now-state)
+                         (if (and (= 0 (length notes1))
+                                  (= 0 (length notes2)))
+                             (analyse-synced-silence)))
+
+                        (else ;; not synchronized
+                         (let* ((vss
+                                 (current-or-previous-voice-states now-state))
+                                (vs1 (car vss))
+                                (vs2 (cdr vss)))
+                           (if (and
+                                (or (not vs1) (= 0 (length (note-events vs1))))
+                                (or (not vs2) (= 0 (length (note-events vs2)))))
+                               (analyse-unsynced-silence vs1 vs2))))
+                        )))
+            (analyse-a2 (1+ result-idx)))))
 
     (define (analyse-solo12 result-idx)
 
       (define (previous-config vs)
-	(let* ((pvs (previous-voice-state vs))
-	       (spi (if pvs (split-index pvs) #f))
-	       (prev-split (if spi (vector-ref result spi) #f)))
-	  (if prev-split
-	      (configuration prev-split)
-	      'apart)))
+        (let* ((pvs (previous-voice-state vs))
+               (spi (if pvs (split-index pvs) #f))
+               (prev-split (if spi (vector-ref result spi) #f)))
+          (if prev-split
+              (configuration prev-split)
+              'apart)))
 
       (define (put-range x a b)
-	;; (display (list "put range "	x a b "\n"))
-	(do ((i a (1+ i)))
-	    ((> i b) b)
-	  (set! (configuration (vector-ref result i)) x)))
+        ;; (display (list "put range "  x a b "\n"))
+        (do ((i a (1+ i)))
+            ((> i b) b)
+          (set! (configuration (vector-ref result i)) x)))
 
       (define (put x)
-	;; (display (list "putting "  x "\n"))
-	(set! (configuration (vector-ref result result-idx)) x))
+        ;; (display (list "putting "  x "\n"))
+        (set! (configuration (vector-ref result result-idx)) x))
 
       (define (current-voice-state now-state voice-num)
-	(define vs ((if (= 1 voice-num) car cdr)
-		    (voice-states now-state)))
-	(if (or (not vs) (equal? (when now-state) (when vs)))
-	    vs
-	    (previous-voice-state vs)))
+        (define vs ((if (= 1 voice-num) car cdr)
+                    (voice-states now-state)))
+        (if (or (not vs) (equal? (moment now-state) (moment vs)))
+            vs
+            (previous-voice-state vs)))
 
       (define (try-solo type start-idx current-idx)
-	"Find a maximum stretch that can be marked as solo.  Only set
+        "Find a maximum stretch that can be marked as solo.  Only set
 the mark when there are no spanners active.
 
       return next idx to analyse.
 "
-	(if (< current-idx (vector-length result))
-	    (let* ((now-state (vector-ref result current-idx))
-		   (solo-state (current-voice-state now-state (if (equal? type 'solo1) 1 2)))
-		   (silent-state (current-voice-state now-state (if (equal? type 'solo1) 2 1)))
-		   (silent-notes (if silent-state (note-events silent-state) '()))
-		   (solo-notes (if solo-state (note-events solo-state) '())))
-	      ;; (display (list "trying " type " at "  (when now-state) solo-state silent-state	 "\n"))
-	      (cond ((not (equal? (configuration now-state) 'apart))
-		     current-idx)
-		    ((> (length silent-notes) 0) start-idx)
-		    ((not solo-state)
-		     (put-range type start-idx current-idx)
-		     current-idx)
-		    ((and
-		      (null? (span-state solo-state)))
-
-		     ;;
-		     ;; This includes rests. This isn't a problem: long rests
-		     ;; will be shared with the silent voice, and be marked
-		     ;; as unisilence. Therefore, long rests won't
-		     ;;	 accidentally be part of a solo.
-		     ;;
-		     (put-range type start-idx current-idx)
-		     (try-solo type (1+ current-idx) (1+  current-idx)))
-		    (else
-		     (try-solo type start-idx (1+ current-idx)))))
-	    ;; try-solo
-	    start-idx))
-
-      (define (analyse-moment result-idx)
-	"Analyse 'apart starting at RESULT-IDX.  Return next index."
-	(let* ((now-state (vector-ref result result-idx))
-	       (vs1 (current-voice-state now-state 1))
-	       (vs2 (current-voice-state now-state 2))
-	       ;; (vs1 (car (voice-states now-state)))
-	       ;; (vs2 (cdr (voice-states now-state)))
-	       (notes1 (if vs1 (note-events vs1) '()))
-	       (notes2 (if vs2 (note-events vs2) '()))
-	       (n1 (length notes1))
-	       (n2 (length notes2)))
-	  ;; (display (list "analyzing step " result-idx "  moment " (when now-state) vs1 vs2  "\n"))
-	  (max
-	   ;; we should always increase.
-	   (cond ((and (= n1 0) (= n2 0))
-		  (put 'apart-silence)
-		  (1+ result-idx))
-		 ((and (= n2 0)
-		       (equal? (when vs1) (when now-state))
-		       (null? (previous-span-state vs1)))
-		  (try-solo 'solo1 result-idx result-idx))
-		 ((and (= n1 0)
-		       (equal? (when vs2) (when now-state))
-		       (null? (previous-span-state vs2)))
-		  (try-solo 'solo2 result-idx result-idx))
-
-		 (else (1+ result-idx)))
-	   ;; analyse-moment
-	   (1+ result-idx))))
+        (if (< current-idx (vector-length result))
+            (let* ((now-state (vector-ref result current-idx))
+                   (solo-state (current-voice-state now-state (if (equal? type 'solo1) 1 2)))
+                   (silent-state (current-voice-state now-state (if (equal? type 'solo1) 2 1)))
+                   (silent-notes (if silent-state (note-events silent-state) '()))
+                   (solo-notes (if solo-state (note-events solo-state) '())))
+              ;; (display (list "trying " type " at "  (moment now-state) solo-state silent-state        "\n"))
+              (cond ((not (equal? (configuration now-state) 'apart))
+                     current-idx)
+                    ((> (length silent-notes) 0) start-idx)
+                    ((not solo-state)
+                     (put-range type start-idx current-idx)
+                     current-idx)
+                    ((and
+                      (null? (span-state solo-state)))
+
+                     ;;
+                     ;; This includes rests. This isn't a problem: long rests
+                     ;; will be shared with the silent voice, and be marked
+                     ;; as unisilence. Therefore, long rests won't
+                     ;;  accidentally be part of a solo.
+                     ;;
+                     (put-range type start-idx current-idx)
+                     (try-solo type (1+ current-idx) (1+  current-idx)))
+                    (else
+                     (try-solo type start-idx (1+ current-idx)))))
+            ;; try-solo
+            start-idx))
+
+      (define (analyse-apart-silence result-idx)
+        "Analyse 'apart-silence starting at RESULT-IDX.  Return next index."
+        (let* ((now-state (vector-ref result result-idx))
+               (vs1 (current-voice-state now-state 1))
+               (vs2 (current-voice-state now-state 2))
+               (rests1 (if vs1 (rest-or-skip-events vs1) '()))
+               (rests2 (if vs2 (rest-or-skip-events vs2) '()))
+               (prev-state (if (> result-idx 0)
+                               (vector-ref result (- result-idx 1))
+                               #f))
+               (prev-config (if prev-state
+                                (configuration prev-state)
+                                'apart-silence)))
+          (cond
+           ;; rest with multi-measure rest: choose the rest
+           ((and (synced? now-state)
+                 (= 1 (length rests1))
+                 (ly:in-event-class? (car rests1) 'rest-event)
+                 (= 0 (length rests2))) ; probably mmrest
+            (put 'silence1))
+
+           ;; as above with parts swapped
+           ((and (synced? now-state)
+                 (= 1 (length rests2))
+                 (ly:in-event-class? (car rests2) 'rest-event)
+                 (= 0 (length rests1))) ; probably mmrest
+            (put 'silence2))
+
+           ((synced? now-state)
+            (put 'apart-silence))
+
+           ;; remain in the silence1/2 states until resync
+           ((equal? prev-config 'silence1)
+            (put 'silence1))
+
+           ((equal? prev-config 'silence2)
+            (put 'silence2))
+
+           (else
+            (put 'apart-silence)))
+
+          (1+ result-idx)))
+
+      (define (analyse-apart result-idx)
+        "Analyse 'apart starting at RESULT-IDX.  Return next index."
+        (let* ((now-state (vector-ref result result-idx))
+               (vs1 (current-voice-state now-state 1))
+               (vs2 (current-voice-state now-state 2))
+               ;; (vs1 (car (voice-states now-state)))
+               ;; (vs2 (cdr (voice-states now-state)))
+               (notes1 (if vs1 (note-events vs1) '()))
+               (notes2 (if vs2 (note-events vs2) '()))
+               (n1 (length notes1))
+               (n2 (length notes2)))
+          ;; (display (list "analyzing step " result-idx "  moment " (moment now-state) vs1 vs2  "\n"))
+          (max
+           ;; we should always increase.
+           (cond ((and (= n1 0) (= n2 0))
+                  ;; If we hit this, it means that the previous passes
+                  ;; have designated as 'apart what is really
+                  ;; 'apart-silence.
+                  (analyse-apart-silence result-idx))
+                 ((and (= n2 0)
+                       (equal? (moment vs1) (moment now-state))
+                       (null? (previous-span-state vs1)))
+                  (try-solo 'solo1 result-idx result-idx))
+                 ((and (= n1 0)
+                       (equal? (moment vs2) (moment now-state))
+                       (null? (previous-span-state vs2)))
+                  (try-solo 'solo2 result-idx result-idx))
+
+                 (else (1+ result-idx)))
+           ;; analyse-moment
+           (1+ result-idx))))
 
       (if (< result-idx (vector-length result))
-	  (if (equal? (configuration (vector-ref result result-idx)) 'apart)
-	      (analyse-solo12 (analyse-moment result-idx))
-	      (analyse-solo12 (1+ result-idx))))) ; analyse-solo12
+          (let ((conf (configuration (vector-ref result result-idx))))
+            (cond
+             ((equal? conf 'apart)
+              (analyse-solo12 (analyse-apart result-idx)))
+             ((equal? conf 'apart-silence)
+              (analyse-solo12 (analyse-apart-silence result-idx)))
+             (else
+              (analyse-solo12 (1+ result-idx))))))) ; analyse-solo12
 
     (analyse-spanner-states voice-state-vec1)
     (analyse-spanner-states voice-state-vec2)
     (if #f
-	(begin
-	  (display voice-state-vec1)
-	  (display "***\n")
-	  (display voice-state-vec2)
-	  (display "***\n")
-	  (display result)
-	  (display "***\n")))
+        (begin
+          (display voice-state-vec1)
+          (display "***\n")
+          (display voice-state-vec2)
+          (display "***\n")
+          (display result)
+          (display "***\n")))
 
     ;; Extract all forced combine strategies, i.e. events inserted by
     ;; \partcombine(Apart|Automatic|SoloI|SoloII|Chords)[Once]
@@ -560,23 +747,169 @@ the mark when there are no spanners active.
     (analyse-solo12 0)
     ;; (display result)
     (set! result (map
-		  ;; forced-configuration overrides, if it is set
-		  (lambda (x) (cons (when x) (or (forced-configuration x) (configuration x))))
-		  (vector->list result)))
+                  ;; forced-configuration overrides, if it is set
+                  (lambda (x) (cons (moment x) (or (forced-configuration x) (configuration x))))
+                  (vector->list result)))
     (if #f ;; pc-debug
-	 (display result))
+        (display result))
     result))
 
+(define-public default-part-combine-mark-state-machine
+  ;; (current-state . ((split-state-event .
+  ;;                      (output-voice output-event next-state)) ...))
+  '((Initial . ((solo1   . (solo   SoloOneEvent Solo1))
+                (solo2   . (solo   SoloTwoEvent Solo2))
+                (unisono . (shared UnisonoEvent Unisono))))
+    (Solo1   . ((apart   . (#f     #f           Initial))
+                (chords  . (#f     #f           Initial))
+                (solo2   . (solo   SoloTwoEvent Solo2))
+                (unisono . (shared UnisonoEvent Unisono))))
+    (Solo2   . ((apart   . (#f     #f           Initial))
+                (chords  . (#f     #f           Initial))
+                (solo1   . (solo   SoloOneEvent Solo1))
+                (unisono . (shared UnisonoEvent Unisono))))
+    (Unisono . ((apart   . (#f     #f           Initial))
+                (chords  . (#f     #f           Initial))
+                (solo1   . (solo   SoloOneEvent Solo1))
+                (solo2   . (solo   SoloTwoEvent Solo2))))))
+
+(define-public (make-part-combine-marks state-machine split-list)
+  "Generate a sequence of part combiner events from a split list"
+
+  (define (get-state state-name)
+    (assq-ref state-machine state-name))
+
+  (let ((full-seq '()) ; sequence of { \context Voice = "x" {} ... }
+        (segment '()) ; sequence within \context Voice = "x" {...}
+        (prev-moment ZERO-MOMENT)
+        (prev-voice #f)
+        (state (get-state 'Initial)))
+
+    (define (commit-segment)
+      "Add the current segment to the full sequence and begin another."
+      (if (pair? segment)
+          (set! full-seq
+                (cons (make-music 'ContextSpeccedMusic
+                                  'context-id (symbol->string prev-voice)
+                                  'context-type 'Voice
+                                  'element (make-sequential-music (reverse! segment)))
+                      full-seq)))
+      (set! segment '()))
+
+    (define (handle-split split)
+      (let* ((moment (car split))
+             (action (assq-ref state (cdr split))))
+        (if action
+            (let ((voice (car action))
+                  (part-combine-event (cadr action))
+                  (next-state-name (caddr action)))
+              (if part-combine-event
+                  (let ((dur (ly:moment-sub moment prev-moment)))
+                    ;; start a new segment when the voice changes
+                    (if (not (eq? voice prev-voice))
+                        (begin
+                          (commit-segment)
+                          (set! prev-voice voice)))
+                    (if (not (equal? dur ZERO-MOMENT))
+                        (set! segment (cons (make-music 'SkipEvent
+                                                          'duration (make-duration-of-length dur)) segment)))
+                    (set! segment (cons (make-music part-combine-event) segment))
+
+                    (set! prev-moment moment)))
+              (set! state (get-state next-state-name))))))
+
+    (for-each handle-split split-list)
+    (commit-segment)
+    (make-sequential-music (reverse! full-seq))))
+
+(define-public default-part-combine-context-change-state-machine-one
+  ;; (current-state . ((split-state-event . (output-voice next-state)) ...))
+  '((Initial . ((apart         . (one    . Initial))
+                (apart-silence . (one    . Initial))
+                (apart-spanner . (one    . Initial))
+                (chords        . (shared . Initial))
+                (silence1      . (shared . Initial))
+                (silence2      . (null   . Demoted))
+                (solo1         . (solo   . Initial))
+                (solo2         . (null   . Demoted))
+                (unisono       . (shared . Initial))
+                (unisilence    . (shared . Initial))))
+
+    ;; After a part has been used as the exclusive input for a
+    ;; passage, we want to use it by default for unisono/unisilence
+    ;; passages because Part_combine_iterator might have killed
+    ;; multi-measure rests in the other part.  Here we call such a
+    ;; part "promoted".  Part one begins promoted.
+    (Demoted . ((apart         . (one    . Demoted))
+                (apart-silence . (one    . Demoted))
+                (apart-spanner . (one    . Demoted))
+                (chords        . (shared . Demoted))
+                (silence1      . (shared . Initial))
+                (silence2      . (null   . Demoted))
+                (solo1         . (solo   . Initial))
+                (solo2         . (null   . Demoted))
+                (unisono       . (null   . Demoted))
+                (unisilence    . (null   . Demoted))))))
+
+(define-public default-part-combine-context-change-state-machine-two
+  ;; (current-state . ((split-state-event . (output-voice next-state)) ...))
+  '((Initial . ((apart         . (two    . Initial))
+                (apart-silence . (two    . Initial))
+                (apart-spanner . (two    . Initial))
+                (chords        . (shared . Initial))
+                (silence1      . (null   . Initial))
+                (silence2      . (shared . Promoted))
+                (solo1         . (null   . Initial))
+                (solo2         . (solo   . Promoted))
+                (unisono       . (null   . Initial))
+                (unisilence    . (null   . Initial))))
+
+    ;; See the part-one state machine for the meaning of "promoted".
+    (Promoted . ((apart         . (two    . Promoted))
+                 (apart-silence . (two    . Promoted))
+                 (apart-spanner . (two    . Promoted))
+                 (chords        . (shared . Promoted))
+                 (silence1      . (null   . Initial))
+                 (silence2      . (shared . Promoted))
+                 (solo1         . (null   . Initial))
+                 (solo2         . (solo   . Promoted))
+                 (unisono       . (shared . Promoted))
+                 (unisilence    . (shared . Promoted))))))
+
+(define-public (make-part-combine-context-changes state-machine split-list)
+  "Generate a sequence of part combiner context changes from a split list"
+
+  (define (get-state state-name)
+    (assq-ref state-machine state-name))
+
+  (let ((change-list '())
+        (prev-voice #f)
+        (state (get-state 'Initial)))
+
+    (define (handle-split split)
+      (let* ((moment (car split))
+             (action (assq-ref state (cdr split))))
+        (if action
+            (let ((voice (car action))
+                  (next-state-name (cdr action)))
+              (if (not (eq? voice prev-voice))
+                  (begin
+                    (set! change-list (cons (cons moment voice) change-list))
+                    (set! prev-voice voice)))
+              (set! state (get-state next-state-name))))))
+
+    (for-each handle-split split-list)
+    (reverse! change-list)))
 
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
-(define-public (add-quotable parser name mus)
+(define-public (add-quotable name mus)
   (let* ((tab (eval 'musicQuotes (current-module)))
          (voicename (get-next-unique-voice-name))
          ;; recording-group-emulate returns an assoc list (reversed!), so
          ;; hand it a proper unique context name and extract that key:
          (ctx-spec (context-spec-music mus 'Voice voicename))
-         (listener (ly:parser-lookup parser 'partCombineListener))
+         (listener (ly:parser-lookup 'partCombineListener))
          (context-list (reverse (recording-group-emulate ctx-spec listener)))
          (raw-voice (assoc voicename context-list))
          (quote-contents (if (pair? raw-voice) (cdr raw-voice) '())))