Represents a musical voice
MusicVoice[{measure1, measure2, …}]
MusicVoice[{event1, event2, …}]
MusicVoice[{{event11, event12, …}, {event21, event22, …}}]
MusicVoice[events, ts, ks]
MusicVoice[events, ts, ks, properties]
MusicVoice[music, events, ts, ks, properties]