In a fugue, the exposition is "the statement of the subject in imitation by the several voices; especially the first such statement, with which the fugue begins."
Exposition in classical sonata form
The term is most widely used as an analytical convenience to denote a portion of a movement identified as an example of classical tonal sonata form. The exposition typically establishes the music's tonic key, and then modulates to, and ends in, the dominant. If the exposition starts in a minorkey, it typically modulates to the relative major key. There are many exceptions, especially in the late Classical and Romantic era. For example, to the mediant, the flat mediant, the dominant when in a minor key, the minor dominant, the submediant, the relative minor, or the parallel major. Saint-Saens' Piano Concerto No. 3 even modulates to the leading tone in its first movement exposition, with no orchestral accompaniment. On the other hand, other Classical and Romantic composers strictly adhered to the traditional scheme of modulating to the dominant in a major key or the relative major in a minor key, including Haydn, Mozart, Hummel, John Field, and Mendelssohn. The exposition may include identifiable musical themes, and may develop them, but it is usually the key relationships and the sense of "arrival" at the dominant that is used by analysts in identifying the exposition. The exposition in classical symphonies is typically repeated, although there are many examples where the composer does not specify such a repeat, and it never is repeated in concertos. In the recapitulation, the material in the exposition is repeated or paraphrased either in the home key, or the parallel major of the home key if it is minor, although as with the exposition, a different modulation may be used. If the movement starts with an introductory section, this introduction is not usually analysed as being part of the movement's exposition. In many works of the Classical period and some of the Romantic era, the exposition is often bracketed by repeat signs, indicating that it is to be played twice. This is something which is not always done in concert from the 20th Century onwards.
Exposition in fugue form
A fugue usually has two main sections: the exposition and the body. In the exposition, each voice plays its own adaptation of the theme, in either a subject or an answer; they also provide countersubjects to the following voices as they enter. The exposition usually ends on either a I or V chord, and is then followed by the body.
