How many voices are used in Bach’s St. Anne Fugue?

Johann Sebastian Bach’s Fugue in E-flat Major for organ, BWV 552, commonly known as the St. Anne fugue, is a five-voice fugue.1

While it is classified as a five-voice composition, it does not maintain a complete texture of five parts throughout the entire piece. Instead, the work features passages of two, three, or four parts, which make up the majority of the fugue's duration.1