The American Federation of Musicians defines arranging as "the art of preparing and adapting an already written composition for presentation in other than its original form. An arrangement may include reharmonization, paraphrasing, and/or development of a composition, so that it fully represents the melodic, harmonic, and rhythmic structure".[1] Jazz arrangers often take music written for other forms like popular music, religious music, or classical music and alter the tempo, rhythm, and the chord structure to re-create music for a jazz idiom. They can also take so-called head arrangements and commit them to paper.