The Swiss Army Bass

"Yup-that's right. It's a bass guitar with a midi keyboard mounted on it. Yes, the two are played simultaneously. The bass is played with the left hand alone by means of a guitar technique known as “hammer-ons” while the keyboard (which emulates a distorted slide guitar most of the time. among other things) is played with the right hand. This instrument has a weight equivalent to that of a small motorcycle, and as you might imagine, requires years of time and patience to 'master'."

click here for more including some video. Also check out The Droning Betsy. via cebec who found it on Ektopia.