Computer Music in Squeak

We have an annual 'Hands-On Science' week in the summer holiday,
when high-school pupils from around the country come and try things.
There are 'projects' where we have them for 3 or 4 mornings and 'snacks'
where we have them for a couple of hours.
I received an unexpected request to run another one this coming summer
(it's winter here now).  It suddently occurred to me that a computer
music project using Squeak should be really fun, but I've never done
anything like that.

Any suggestions would be MOST welcome.   It may not come off, but if it
does it should be quite enjoyable for the students.  We'd probably have
a lab of OS/X macintoshes, if it makes any difference.