via
this auction
"This is a professionally circuit-bent Realistic Concertmate 500, which is the same synth as the famed Casio SK-1, just sold under a different brand name.
It was circuit bent by Diabolical Devices in the US, who are famed all over the world for their circuit-bending prowess.
It features a 20 point patch bay, 6 mystery switches on the side that muzz up the sound and cause all sorts of strange effects.
The patch bay allows you to connect one part of the circuit with another, to produce strange mutations in the sound generation process. You can't damage the machine like this.
It has an internal LFO (controlled by the second large knob from the left) that is patchable to any of the points via the purple patch hole, and a light sensor on the right whose sensitivity is controlled by the leftmost big knob.
This is also patchable into the bay via the blue patch hole.
The two metal switches on the far right control whether these controls are active or not, and this is indicated by the lights next to them turning blue or red.
As with all circuit bent devices, some combinations will crash the keyboard and you'll have to restart it - possibly also sticking on some amazing sound in the process.
The best thing is just to play around until you get something good, then record it.
All the normal Casio SK-1 functions are still active - with all the controls turned off, and no patches, this is just like a regular SK-1.
It comes with three high-quality patch cables, and a power adaptor (7.5v).
It would be perfect for anyone looking for new and exciting sounds that cannot be made any other way!"
Video of one previously posted
here.