circuit bending is where you take a (usually) battery powered electronic device that makes sounds, like toy instruments, keyboards, speak and spell,
etc. and open it up, make a jumper (i use 2 jeweler's screwdrivers connected with a wire and alligator clips) then you start probing the circuit board for different connections, and short circuits, that will either change the existing sound, or create new sounds that the toy was never supposed to make.
after mapping the new "circuits", you need to find ways to operate the new sounds. this is usually done by soldering switches, knobs, potentiometers, photo cells etc. to the new connections.
if you do an internet search you will find all kinds of crazy stuff.
Reed Ghazala is credited as it's originator, and has written a basic "how to" book on the subject...
my friend has the saw at his place, i will try to get pics next time i see him...
it was a "home depot" toy chainsaw from toys r us, repainted...(yes, it is covered in blood :wink: )