for queuing audio "commands" which is a much nicer way to interact
with the audio system in general in a more complex application, as this
lets you play audio in more of a "fire and forget" kind of way.
Rc<AudioBuffer> play methods provided as an alternative because
otherwise you end up with a somewhat gross double-copy of the audio
buffer being played. but i didn't want to necessarily force use of
Rc<AudioBuffer> just yet ... thus both versions of these methods are
provided.
Gered