Buy a kit from here and build it
http://www.paia.com/
More specifically....try building these kits
http://www.paia.com/p9700s.htm &
http://www.paia.com/fatman.htm
Once you have the ability to build these (all parts are included...you just need to assemble it)...your then in a better postion to think about designing your own analog mono synth. And before you ask...to the best of my knowledge there ar eno analog poly kits (yet)
Here check out this site
http://www.unease.se/paiabuild.htm The guy from there built a P9700S and made some demo MP3's!
Cheers
DS