Tristan Perich's 1-Bit Symphony is an electronic composition in five movements on a single microchip.
Though housed in a CD jewel case like his first circuit album (1-Bit Music 2004-05), 1-Bit Symphony is not a recording in the traditional sense; it literally "performs" its music live when turned on. A complete electronic circuit—programmed by the artist and assembled by hand—plays the music through a headphone jack mounted into the case itself.
More on the project website, here. The project will be released next week via Cantaloupe Music. You can order it here for $29 plus shipping.
Update: Pesco blogged about an earlier iteration of this project back in 2005.
(Thanks, Marianne Shaneen!)