The Beatles song 12-Bar Original was recorded in 1965 at the Abbey Road studios. It is essentially an informal Beatles jam session, improvised for fun as an instrumental.
Producer George Martin liked what he was hearing, and started the recording equipment. He asked the group to play it another time, and take 2 was archived.
The recording never made its way into an album during the time the Beatles were together. In 1996, when the Anthology 2 collection was compiled from various takes made during Abbey Road recording sessions, 12-Bar-Original became available to the public for the first time.
Ringo later commented that the song had been written by all four members of the group, and Lennon later referred to it as some "lousy 12-bar." The use of the word "written" is somewhat inapposite because the song was essentially a series of improvisations based on the 12-bar blues format and thus resembles a "theme-and-variations" format found in classical music.
Because of its improvisational, jam-session quality, the song is credited to all four Beatles as composers, one of only a handful of Beatles instrumentals. Click here for a list of the Beatles instrumentals.
Take two of 12-Bar-Original was over 6½ minutes long prior to editing for the Anthology 2 album.