A fugue is a musical composition characterized by the systematic repetition of a principal theme (subject) in simultaneous lines (voices). It is a complex form of counterpoint, where the subject is introduced by one voice and then imitated by others at different pitches. It is related to contrapuntal forms such as a Canon, but unlike a strict canon, where voices follow the same melody at fixed intervals, a fugue introduces a subject that is answered and developed through varied entries across voices.
Commonly used in classical music, a fugue typically consists of an exposition, where the subject is presented, followed by episodes that develop the theme through variations and counter-subjects. The structure allows for intricate interplay between voices, creating a rich tapestry of sound.