(Sonata form, first movement form) Most commonly the first movement of a classical sonata (and symphony, quartet, trio) is in sonata form. (In concertos, the sonata-form first movement is somewhat less rigid than it would be in a sonata or symphony.) It consists of three sections: “exposition” with two themes in the tonic and the dominant respectively, a modulating “development” of both themes, and a “recapitulation” of both themes in the tonic. The sonata form is considered either a ternary form (A B A) the opening section itself being in binary form; or more appropriately, an extended, rounded, open binary form (A B) the exposition being the first half (and repeated), and the development and the recapitulation the second half (also repeated in earlier examples). In the exposition, two musical ideas are presented: the first subject (in tonic) and the second subject (in dominant/relative major) linked with a ‘bridging passage’ and a closing group at the end. In the development these musical ideas are extended, detailed and developed usually with much explorations of new keys and staying away from the tonic. New material may be presented (the Eroica, the Farewell). In the recapitulation both subjects and the original key return (double return). In a minor key, the second subject is now in the tonic minor instead of its relative major. This also requires modification of the bridge passage. There may be a coda at the end. One of the advantages of the sonata form is that the construction of new themes should consider their capability for development. A dramatic aspect of this form is the differing characters (rhythmic-masculine first subject and feminine-lyrical second subject) and opposing keys of the themes in the exposition (tonal contrast). The form is designed to create anticipation as it proceeds. The abridged sonata form, used in slow movements (the Unfinished symphony) and classical overtures, lacks the development (A-B-A-B-coda). As in the sonata form, the B section should be in the dominant or a substitute dominant.