I have an alerting application where I need a TTS application to play a wav file
prior to speaking the text. There are multiple wav files, from a simple chime
to a siren, that accompany the text; this rules out hard coding the wav file
into the TTS application. Clearly I'll need to build both a new client and TTS
application. My question is regarding the schema to use.

Is there a single schema that can communicate both speech and wav files? If
not, do you think I should extend the tts.speak to include attributes for intro
audio files or should I create a totally new schema for the combination (e.g.
tts.alert)? I think it is a bad idea to try sending separate messages because
UDP does not guarantee sequenced delivery and it would require a complicated
client that knows to wait for multiple messages from different schemas. As an
alternative, is it possible to encapsulate two different schemas in the same
message (e.g. tts.speak and Playlist.Track)?