Typical big band arrangements are written in strophic form with the same phrase and chord structure repeated several times. Each iteration, or chorus, commonly follows twelve bar blues form or thirty-two-bar (AABA) song form. The first chorus of an arrangement introduces the melody and is followed by choruses of development. This development may take the form of improvised solos, written soli sections, and "shout choruses".
An arrangement's first chorus is sometimes preceded by an introduction, which may be as short as a few measures or may extend to chorus of its own. Many arrangements contain an interlude, often similar in content to the introduction, inserted between some or all choruses. Other methods of embellishing the form include modulations and cadential extensions.
Some big ensembles, like King Oliver's, played music that was half-arranged, half-improvised, often relying on head arrangements. A head arrangement is a piece of music that is formed by band members during rehearsal. They experiment, then memorize the way they are going to perform the piece, without writing it on sheet music. During the 1930s, Count Basie's band often used head arrangements, as Basie said, "we just sort of start it off and the others fall in."