Well... you'd be better off building it in Director for a start,
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it offers ridiculously precise, realtime control of audio... with an almost infinite amount of virtual tracks.
So yeah... sound toys, these were really popular in the mid/late '90's and early '00's, and were frequently distributed on Creative Review CD-ROM's, so it might be worth seeing if your local Uni Library has copies of these.
I'd definitely advise that you try and source some of the following for research purposes though;
Coldcut - Let Us Play! As that featured an interactive sound toy, that was groundbreaking for it's time.
Afro Celt Soundsystem - Volume 2: Release Featured a really clever and intuitive sequencer that allowed the user to assemble their own Afro Celt songs by using samples, it automatically sync'd them too.
Antirom's - Fruitpencer Was a simple 'fruit based' (think like a one armed band type of thing) sequencer that assigned indiviual sounds to specific fruits, and the fruits could be changed creating simple songs, the temp could be changed too.
Speaking of Antirom, you could do worse than track down their 'Antirom CD-ROM' from 1995, though your best bet is seeing if your Uni library has a copy as they're uber-rare.
Tomato One, Two, 3 Are well worth tracking down, especially the
latter, that had some interesting interactivity and use of sounds on it.
Tomato Interactive, also produced a really fresh website for Mitsubishi Motors in 2000 I think it was, but I can't remember the URL off the top of my head, but I'll have a tommy gander in some old design mags and I'll let you know.
It might be worth trawlling through
Fabrica's site, as they used to have a section devoted to innovative little sound toys.
There's plenty more, but my memory's a little fuzzy.