The Musical Offering in the context of Frederick the Great

In classical music, a fugue (/fjuːɡ/, from Latin fuga, meaning 'flight' or 'escape') is a contrapuntal, polyphonic compositional technique in two or more voices, built on a subject (a musical theme) that is introduced at the beginning in imitation (repetition at different pitches), which recurs frequently throughout the course of the composition. It is not to be confused with a fuguing tune, which is a style of song popularized by and mostly limited to early American (i.e. shape note or "Sacred Harp") music and West Gallery music. A fugue usually has three main sections: an exposition, a development, and a final entry that contains the return of the subject in the fugue's tonic key. Fugues can also have episodes, which are parts of the fugue where new material often based on the subject is heard; a stretto (plural stretti), when the fugue's subject overlaps itself in different voices, or a recapitulation. A popular compositional technique in the Baroque era, the fugue was fundamental in showing mastery of harmony and tonality as it presented counterpoint.

In the Middle Ages, the term was widely used to denote any works in canonic style; however, by the Renaissance, it had come to denote specifically imitative works. Since the 17th century, the term fugue has described what is commonly regarded as the most fully developed procedure of imitative counterpoint.

Compositions by Johann Sebastian Bach printed during his lifetime (1685–1750) include works for keyboard instruments, such as his Clavier-Übung volumes for harpsichord and for organ, and to a lesser extent ensemble music, such as the trio sonata of The Musical Offering, and vocal music, such as a cantata published early in his career. Other works, such as several canons, were printed without an indication by which instruments they were to be performed.

No more than a few works by Johann Sebastian Bach were printed during his lifetime. Extended works for choir and instrumentalists were not printed very often in his day. Bach selected mostly keyboard compositions for publication, which conformed to such contemporary practices, and was instrumental in establishing him as a keyboard composer. His works not only circulated in print: also manuscripts were copied and transmitted. Whether or not a work was selected for print was independent of the quality of the music.