audio "device". Since the OS X version of SC
likely uses CoreAudio (a
callback-based library) and since the source for prior versions is
unavailable, you may be able to do the port of the audio engine
straightforwardly.
FWIW, AFAIK, SC has always been written around an interrupt+callback
design. on MacOS (< X), the audio "thread" of SC actually runs in OS
interrupt context (a bit limiting and, ahem, a bit dangerous).
--p