In music

Music

Music is an art form whose medium is sound and silence. Its common elements are pitch , rhythm , dynamics, and the sonic qualities of timbre and texture...

, arch form is a section

Section (music)

In music, a section is "a complete, but not independent musical idea". Types of sections include the introduction or intro, exposition, recapitulation, verse, chorus or refrain, conclusion, coda or outro, fadeout, bridge or interlude...

al structure

Musical form

The term musical form refers to the overall structure or plan of a piece of music, and it describes the layout of a composition as divided into sections...

 for a piece of music based on repetition

Repetition (music)

Repetition is important in music, where sounds or sequences are often repeated. One often stated idea is that repetition should be in balance with the initial statements and variations in a piece. It may be called restatement, such as the restatement of a theme...

, in reverse order, of all or most musical sections such that the overall form is symmetric, most often around a central movement. The sections need not be repeated verbatim but must at least share thematic

Theme (music)

In music, a theme is the material, usually a recognizable melody, upon which part or all of a composition is based.-Characteristics:A theme may be perceivable as a complete musical expression in itself, separate from the work in which it is found . In contrast to an idea or motif, a theme is...

 material.

It creates interest through interplay among "memory, variation, and progression." Though the form appears to be static and to deny progress, the pairs of movements create a "unidirectional process" with the center, 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

Béla Bartók

Béla Viktor János Bartók was a Hungarian composer and pianist. He is considered one of the most important composers of the 20th century and is regarded, along with Liszt, as Hungary's greatest composer...

 is noted for his use of arch form, e.g., in his Fourth and Fifth string quartets, Concerto for Orchestra

Concerto for Orchestra (Bartók)

Concerto for Orchestra, Sz. 116, BB 123, is a five-movement musical work for orchestra composed by Béla Bartók in 1943. It is one of his best-known, most popular and most accessible works. The score is inscribed "15 August – 8 October 1943", and it premiered on December 1, 1944 in Boston Symphony...

, Second Piano Concerto, and, less so, Second Violin Concerto (ibid). Samuel Barber

Samuel Barber

Samuel Osborne Barber II was an American composer of orchestral, opera, choral, and piano music. His Adagio for Strings is his most popular composition and widely considered a masterpiece of modern classical music...

's Adagio for Strings

Adagio for Strings

Adagio for Strings is a work by Samuel Barber, arranged for string orchestra from the second movement of his String Quartet, Op. 11. Barber finished the arrangement in 1936, the same year as he wrote the quartet...

and Shostakovich's String Quartet no. 8 in C minor also use arch form.

The most popular arch-form structure is ABCBA.