Ages ago, I built a ribbon controller for driving my Korg Mono/Poly.  Recently, I revived the ribbon and MIDI-fied it.  Then, I brought back its CV capabilities and hooked it up to my Mono/Poly.  It's so fun!

If you're interested, you can check it out (including demo) here:

http://synthhacker.blogspot.com/2016/04/diy-ribbon-controller-cv.html

Has anyone else built a ribbon before

Chip