Circuit bending is new form of audio manipulation that consists of modifying the circuits of electronic devices that generate audio to come up with noisy, experimental and sometimes plain wacky sounds. Opening up everyday kid's toys and short-circuiting its innards is sometimes enough to get surprising results. This includes any low voltage devices like battery-powered toys, small pianos and guitar pedals. Do not attempt to circuit bend AC powered devices unless you know exactly what you are doing.
Many circuit bent toys and devices are on sale on amazon.com and ebay, ranging from demented Furby toys to the classic small Casio Piano for kids is one of the most popular instruments to circuit-bend, partly because it's internals are easily accessible.
Most people think you need to know electronics and circuitry to circuit bend, and although it helps, it is not at all necessary. It works like this: You open up the toy (unscrew and pop open to reveal the circuitry), and basically short-circuit the board until you get sounds you like. Many use alligator clips closed on needles to get a surgical-like touch of the board. Don't be afraid to blow a circuit ! It's never happened to me and either way, you should only try this with equipment you don't mind messing around with.
If you want to be able to revert back and forth between the original sound and the bent one, install a basic switch to the connection. If not, you can simply weld a link with a wire from one spot to the other and let it be. Another very popular option is the use of potentiometer to adjust volume, depth or simply to add more noise to the mix !
Some circuit boards can be extremely compact, and it takes some skill to weld in tight spots, but with a bit of practice, anyone can do it. Except maybe Micheal J Fox. I once bent my father's old Yamaha keyboard and came up with such a depraved, crushingly noisy sound, it became my favorite toy. unfortunately I tried welding it to a switch with a few beers in me and ended up making a mess ou of the circuit board and caused irreparable damage.
There are plenty of online forums, websites and videos out there going into detail on how to circuit bend, so go out there and enjoy. Here are a few favorites: