Here he explains how his idea of circuit bending came about:
“The sounds that came from that first short circuit back in the mid 1960’s were just so interesting! This was a mini-amp, 9V, shorting out in my desk drawer. The result was a series of electronic sounds rising in pitch, over and over, like a modern police siren. But back then, of course, sirens were purely mechanical. So there was nothing really to compare this to!
I immediately thought, “If this can happen by accident, what might happen if I started blindly short-circuiting the amp here, there and everywhere? Are there more hidden sounds?” The idea of “toy” or “garbage” never came into my mind. This was magic.
I’ve been a chance artist since a little boy (neighbors thought I was strange, freezing colored liquids in the winter back yard to see the forms they’d take). Recognizing another chance art here was easy. Bending sonically explains chance the way Suminagashi and dye migration explain visually. All of these “sound” the same to me – see if you don’t think so.”
If you’re interested in bending, there’s a lot of great stuff in the full interview.