"Circuit bending" is the term for modifying cheap electronics (most often kids' toys) to turn them into musical instruments. (Here's a MAKE video podcast about circuit bending, and here are some MP3s of songs played on circuit-bent instruments.)
On April 12-14, the Bent Festival is coming to Los Angeles. A concert will be will be held at Il Corral on April 12. The April 13-14th events will be held at Velaslavasay Panorama. The event includes workshops (some are free) and sessions with leading artists in the field.
