What is a complex polyphonic instrumental composition popular during the baroque?

A complex polyphonic instrumental composition popular during the Baroque period is the "fugue." Characterized by its intricate interweaving of multiple independent melodies (or voices), a fugue typically begins with a single theme introduced by one voice and then imitated by others at different pitches. Composers like Johann Sebastian Bach elevated the fugue to a high art form, showcasing both technical skill and expressive depth. The structure and counterpoint inherent in fugues exemplify the Baroque emphasis on complexity and ornamentation in music.