BrainModular

A friend of mine just pointed this out to me... Tempting... Might be able to factor into a rig somehow! If nothing else, some pre-built parts!

http://littlebits.cc/kits/synth-kit

I wonder how their bus works...

littleBits and Korg have demystified a traditional analog synthesizer, making it super easy for novices and experts alike to create music.

connects to speakers, computers and headphones
can be used to make your own instruments
fits into the littleBits modular system for infinite combos of audio, visual and sensory experiences

Example:
http://youtu.be/vDxz8bpqOMU

probably just a standardized IO bus not a digital serial, so I haven't seen any computer bus peripherals either even though they say....but you could probably merge with existing DIY stuff like from ucapps.de for MIDI control or even arduino or raspberry pi...just get ahold of the manual and you could probably find the voltage range and current and could do an A/D.

-S

I've also seen a DIY MS20 modular kit and Moog has a build-your own as well.

we have this kit at home. its pretty nice toy. and if you are looking for some io there are lot of modules you can buy. one of modules is arduino...