The Well-Tempered Clavier, Book 1

A fugue is a contrapuntal composition built around a single, clearly defined musical subject that is imitated and developed across multiple independent voices. One voice introduces the subject, and subsequent voices enter successively with an answer (a transposed version of the subject), often accompanied by a recurring countersubject. After the exposition, episodes made from fragments of the subject and countersubject modulate to related keys and prepare further entries. Composers employ devices such as inversion, augmentation, diminution, stretto, and pedal points to intensify the texture and drive form. Fugues appear as stand‑alone keyboard or organ works, as movements in chamber and orchestral music, and as sections within larger vocal or instrumental genres.