Go to get an old Commodore 64 computer and canibalize the SID chip. There is a superp tutorial from Thorsten Klose:

http::/www.ucapps.de)

To control the parameters (midi continous control data), I wrote a patch in max/msp. You may use an other software, that is able to configure midicontrollers or use some hardware.

The patch I use can be downloaded here (click the picture).