Fix with latest lilypond 2.15.30

orchestrallily.ily

@@ -546,7 +546,7 @@ orchestralVoiceTypes = #(define-music-function (parser location types) (list?)
   (cond
       ((and (pair? music) (ly:music? (car music)) (not-null? (cdr music)) (ly:music? (cadr music)))
           ;(ly:message "Part-combine with two music expressions")
-          (oly:staff_handler_internal parser piece name "Staff" (list (make-part-combine-music parser music 0))))
+          (oly:staff_handler_internal parser piece name "Staff" (list (make-part-combine-music parser music #f))))
       ((null? music)
           ;;(ly:warning "Part-combine without any music expressions")
           '())