In music, arch form is a sectional way of structuring a piece of music based on the repetition, in reverse order, of all or most musical sections such that the overall form is symmetrical, most often around a central movement. The sections need not be repeated verbatim but at least must share thematic material. For other uses, see Music (disambiguation). ... Look up section in Wiktionary, the free dictionary. ... The term musical form refers to two related concepts: the type of composition (for example, a musical work can have the form of a symphony, a concerto, or other another generic type -- see Multi-movement forms below) the structure of a particular piece (for example, a piece can be writeen... Repetition is the occurrence of an event which has occurred before. ... Symmetry is a characteristic of geometrical shapes, equations and other objects; we say that such an object is symmetric with respect to a given operation if this operation, when applied to the object, does not appear to change it. ... In music, a theme is the initial or primary melody. ...

It creates interest through an interplay among "memory, variation, and progression." Though it has the appearance of being static and denying progress, the pairs of movements create with the center a "unidirectional process" and the form "actually engenders specific expressive possibilities that would otherwise be unavailable for the work as a whole. (Wilson 1992, p.32)

Béla Bartók is often noted for his use of arch form such as in his Fourth and Fifth quartets, Second Piano Concerto, and, less so, Second Violin Concerto (ibid). A popular work using the arch form is Samuel Barber's Adagio for Strings. Béla Bartók in 1927 Bartok redirects here. ... Samuel Barber, photographed by Carl Van Vechten, 1944 Samuel Osborne Barber (March 9, 1910–January 23, 1981) was an American composer of classical music, best known for his Adagio for Strings. ... Samuel Barber, photographed by Carl Van Vechten, 1944 Adagio for Strings is a piece of classical music for string orchestra, arranged by the American composer Samuel Barber from his first string quartet. ...

Most popular structure = ABCBA

Source

• Wilson, Paul (1992). The Music of Béla Bartók. ISBN 0-300-05111-5.