sonata form

or sonata-allegro form

Form of most first movements and often other movements in musical genres such as the symphony, concerto, string quartet, and sonata. The three parts of sonata form evolved from the binary, or two-part, form prominent in the music of the 17th and early 18th centuries. In sonata form the first part, or exposition, presents the basic thematic material of the movement, which is often divided into two thematic groups, the second being in the dominant key or—if the movement is in a minor key—in the relative major key. The second section, or development, generally treats the earlier themes freely, often moving to various different keys. It leads to the final section, or recapitulation, when the tonic key returns and all the thematic material is repeated in the tonic. Sonata form was the most common form for instrumental works in Western art music from c. 1760 to the early 20th century.

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