Symphophony #1 (video below), a performance at the PixelACHE festival in Helsinki, April 2005, employs Ophones (image above) created by Unsworn. The Ophones are very simply:

a loudspeaker with an attached telephone receiver. When an ophonist has recorded a sound into an ophone, it is repeated infinitely until another sound is recorded into the same ophone.

Watch the video below (windows media format), it’s self explanatory.