A double album is an audio album that spans two units of the primary medium in which it is sold, typically either records or compact disc. A double album is usually, though not always, released as such because the recording is longer than the capacity of the medium. Recording artists often think of double albums as being a single piece artistically; however, there are exceptions such as John Lennon's Some Time in New York City and OutKast's Speakerboxxx/The Love Below .
Since the advent of the compact disc, albums are sometimes released with a bonus disc featuring additional material as a supplement to the main album, with live tracks, studio out-takes, cut songs, or older unreleased material. One innovation was the inclusion of a DVD of related material with a compact disc, such as video related to the album or DVD-Audio versions of the same recordings. Some such discs were also released on a two-sided format called DualDisc.