"One O'Clock Jump" is a jazz standard, a 12-bar blues instrumental, written in 1937 by Count Basie, with arrangement from Eddie Durham and Buster Smith.[citation needed] The original recording of the tune by Basie and his band is noted for the saxophone work of Herschel Evans and Lester Young; trumpeting by Buck Clayton, Walter Page on bass, and Basie himself on piano. "One O'Clock Jump" was the theme song of the Count Basie Orchestra; they used it to close each of their concerts for the next half century. It was reportedly titled "Blue Ball" at first, but a radio announcer feared that title was too risqué. It was listed in the Songs of the Century.
... "Two O'Clock Jump" was a performance by Harry James and his big band in 1939, slightly based on "One O'Clock Jump", but using triplets. Several versions of the original by Harry James and Benny Goodman feature the "Two O'Clock Jump" ending. Lionel Hampton used the song as his theme song for a while as well.
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http://en.wikipedia.org/wiki/One_O'Clock_Jump