Asynchronous sound from MACL

[spector@cs.UMD.EDU (Lee Spector)]

I'm playing sound from MACL with some code, obtained over comp.lang.lisp
about a year ago, which uses _sndplay.  The code now seems to work pretty
well. [When I first got it it refused to play certain snds - I don't know
much about snd formats, but all of the snds played in HyperCard.  Anyway,
I don't seem to have that problem anymore - perhaps it was fixed by the
MACL upgrade to 1.3]

However, I'm now writing something for which I need sounds to be played
while computation continues.  My program is receiving/processing/sending
MIDI data, and I want it to play sounds occasionally from the mac speaker.
However, it is NOT acceptable for the mac to hang, suspending MIDI
processing, while the sound is playing.  

This sort of behavior seems to be the default in HyperCard, so I assume
it can be done from MACL.

Does anyone have sound-playing code that does this?

I'd also appreciate any other pointers, comments, etc, that people have
about playing snds from MACL.

Thanks!  -Lee Spector (spector@cs.umd.edu)