In music, an arrangement refers either to a rewriting of a piece of existing music with additional new material or to a fleshing-out of a compositional sketch, such as a lead sheet. If a musical adaptation does not include new material, it is more accurately termed a transcription.

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" (Corozine 2002, p.3). Orchestration differs in that it is only adapting music for an orchestra or musical ensemble while arranging "involves adding compositional techniques, such as new thematic material for introductions, transitions, or modulations, and endings...Arranging is the art of giving an existing melody musical variety" (ibid).

A satisfactory musical arrangement will most likely (ibid, p.4):

• Provide "contrast between high and low sounds"
• Avoid heavily doubled parts with an emphasis on solo sections
• Be "sufficiently transparent to allow the musical lines to be clearly heard" and
• Not have all the instruments playing throughout.

(ibid, p.4)

Classical music

Arrangements and transcriptions of classical and serious music go back to the early history of this genre. In particular music written for the piano frequently underwent this treatment..Fact: date=July 2008 The suite of ten piano pieces by Modest Mussorgsky Pictures at an Exhibition, has been arranged over twenty times, perhaps the most famous and notable being that of Maurice Ravel.Fact: date=July 2008 Due to a poor grasp of the ability to do so himself, the American composer George Gershwin had his Rhapsody in Blue orchestrated and arranged by Ferde Grofé..Fact: date=July 2008

Popular music

Arrangers in pop music recordings often add parts for orchestral or band instruments involving new material such that the arrangers may reasonably be considered co-composers, although for copyright and royalty purposes usually are not.Fact: date=July 2008 Rhythm section parts are usually improvised or otherwise invented by the performers themselves using chord symbols or a lead sheet as a guide.Fact: date=July 2008 (Rhythm section instruments include guitars, bass guitars, string basses, piano and other keyboard instruments, and drums.)

An existing pop song can be re-recorded with a different arrangement to the original. As well as different instruments, the tempo, time signature and key signature may be altered, sometimes drastically so. The end result is a song that retains familiar phrases and lyrics, but offers something new..Fact: date=July 2008 This practice was particularly popular in the late 1960s. Well known examples of this include Joe Cocker's version of The Beatles' With a Little Help from My Friends, and Ike And Tina Turner's version of Creedence Clearwater Revival's Proud Mary. The American group Vanilla Fudge and British group Yes based their early careers on radical re-arrangements of contemporary hits.Fact: date=July 2008