The full duplex audio should be fine, so long as you do not need the
smallest possible latencies.  Squeak has in fact been designed with
audio applications in mind that need -- e.g., its garbage collector
favors low pause-per-GC instead of low overall CPU percentage.  I know
of some people at GT who built a radio (can't remember if it was AM or
FM) that read files from a swiki and then broadcast them.  This radio
application sounds simpler than what you are doing, but it suggests that
you can build full audio apps in Squeak.

When you say port I/O, is serial port access enough?  If so, Squeak will
do fine for you.  Look at class SerialPort.

These aside, what symptom do you see when you try to play new sounds? 
Do you get silence, static, or a pre-debug window?  I don't know many
programming details of sound programming in Squeak, but if you post more
details maybe someone else will recognize the problem.


Good luck overall!  Squeak should be an excellent platform for you if
you can deal with 1-10 ms latencies; you will be able to tweak your
program very easily, even while it is running.

Lex



PS -- Check out the IRC channel if you have not.  It is EXCELLENT for
people who are starting to use Squeak and thus will bump into all sorts
of oddities and have lots of little questions.