www.geopath.com/~jraden/knobs.html, From the site:
Knob Box DIY project
Last update April 23d, 1999 08:30 am CST
I wanted more real time control over synthesizers. Most synthesizers responds to MIDI continuous controller messages. StampII microprocessor can send MIDI instructions. StampII can read resistances. StampII is easy to program. StampII is fairly cheap.
So I built a box that reads rotary resistors and sends MIDI messages to control synthesizers.
If you build this, please let me know about your experiences. If you come up with a cool mod, send that to me, and I will add it. The whole point for me of making this available is to get help from you improving it.