Plywood with a piezo transducer glued to it under the black box which has a switch and a phono plug. Attached to the board is an old doorbell, two door stops (one weighted with a fishing weight), three screws that are at different depths to tune them in fifths, a baking / cooling rack, a piece of aluminum and a screen door spring. At the bottom of the image is the effects... bass overdrive, ring modulator and a digital delay. Amplified through a Beheringer BX1200 bass amp. The "instrument" is played with my fingers on the screws, a wire brush (both the brush end and the wooden handle) and a bullet vibrator from Babeland (I was at a movie premier in NYC a few weeks ago, Babeland sponsored it. They were handing them out for free and Bugink and I both got one with the intent on using them in this sort of application).
Sound sample here:
Edit: I moved some files around on my server, so the image and MP3 link changed.
Top left: Sousen - four string contraption with a low B bass string and three other strings made of accidentally available wire, and a earth contact to create electronic clicks and buzzes. Sent through delay effect to create loops and rhythms.
Top right: Converted radio with pitch shifter effect (double).
Bottom middle: Electric Morin Khuur (Mongolian two-string instrument) with paired strings (hence four strings instead of two).
I recommend playing your and my MP3 file at the same time.
Ha... you know, this has me thinking... we could do this remotely. It has been done. Send one track, send back two mixed together, return again with a third track mix down, etc.
I have a whole piano worth of strings that I am making something like a koto with. I also have two independent saddle / bridges for bass (instead of a typical bridge with four strings you have one bridge for each string). I am building a two string bass with a B and an E string that I will detune and bow for some extra low end drones.