sound and squeak / siren

hello (and merry xmas!),

i am interested in building a simple experimental musical instrument. i 
am wondering where to look for nice packages of functionality.

i am interested in some quite basic functions:
- sampling/recording sound
- sample playback
- filtering (VST plugin support?)
- MIDI support
- audio visualization

can you point me in the right direction?

so far, i have stumbled upon siren and um0, but are having some troubles 
installing them:

it seems siren is only for visual works? i have downloaded the smalltalk 
package from the siren homepage http://www.create.ucsb.edu/Siren/ , but 
is this importable to/compatible with squeak (and how?)

um0 downloads nicely with the squeakmap package loader, but gives me an 
error during install: can't find EOCD position. what to do?

thanks!

sincerely,

jacob remin