in music, the most mature form of imitative counterpoint (seePOLYPHONY).
The fugue is based on a short melody, or theme, that is stated and developed by two or more voices in turn; once stated, the theme is known as the subject. In the opening section of the fugue, called the exposition, the subject appears sequentially in all the voices, with the first voice stating it in the main key and the second voice stating it in the dominant; this pattern is then repeated. These complementary statements are referred to as subject or answer, or dux and comes (literally, “leader” and “companion”). Occasionally the answer may be in the subdominant, and in the modern fugue it may appear in any key.
The second statement (first imitation) of the subject is followed by a melody that forms a counterpoint to the answer or subject and is called the countersubject. Statements of the subject generally alternate with developmental passages called episodes. Sometimes the brevity of the exposition is counterbalanced by additional statements of the subject and answer, which, when they appear in all voices, constitute the counterexposition.
The middle section of the fugue is devoted to a tonal development of the subject in keys not used in the exposition. It is in the middle section that a strictly polyphonic treatment occurs, with the composer making use of combined counterpoint; the stretto, which is a type of canonical treatment of the subject; or alteration of the subject through, for example, inversion or augmentation. The conclusion of the fugue occurs in the main key and generally takes the form of a recapitulation.
The simple fugue, unlike the sonata form, does not develop a second subject; instead, it concentrates on a single musical idea. This is true even of double and triple fugues (which are based on two or three subjects respectively), since the additional subjects form a kind of extension or complement to the primary subject.
Fugues may be written as independent works; often they are preceded by a prelude, toccata, or a fantasia. Sometimes the fugue is united with the piece that precedes it to form a cycle, as in J. S. Bach’s Well-Tempered Clavier, P. Hindemith’s Ludus Tonalis, and D. D. Shostakovich’s Twenty-four Preludes and Fugues. The fugue may constitute a movement in such cyclic forms as the sonata and oratorio, or it may be a section of a piece in one or more movements.
The fugue developed from such early forms as the canzone and the ricercar (the latter exemplified by the work of G. Gabrieli in the 16th century); it was further developed in the instrumental music of such 17th-century composers as G. Frescobaldi at a time when the major and minor modes were becoming established in the transition from strict to free polyphony. The fugue reached its apex in the work of Bach and G. F. Handel. It appeared less often between the second half of the 18th century and the early 20th century, but such composers as W. A. Mozart, L. van Beethoven, C. Franck, and S. I. Taneev created masterpieces of the form. In the 20th century the fugue has attracted the attention of such composers as I. F. Stravinsky, Hindemith, Shostakovich, and R. K. Shchedrin, who have used it for the expression of innovative musical ideas.