+ (PartCombinePartMusic
+ . ((description . "A part to be combined with other parts on a staff.")
+ (length-callback . ,ly:music-wrapper::length-callback)
+ (start-callback . ,ly:music-wrapper::start-callback)
+ (iterator-ctor . ,ly:part-combine-part-iterator::constructor)
+ (types . (part-combine-part-music music-wrapper-music))
+ ))
+