What is bwv 564?

BWV 564 is a piece of music composed by Johann Sebastian Bach. It is a Prelude and Fugue in E minor for organ and is believed to have been written sometime between 1717 and 1723. The piece is considered one of Bach's most challenging works for organ, featuring intricate counterpoint and demanding technical skill. The Prelude is a fast, virtuosic work, while the Fugue is marked by its complex and elaborate subject. The piece has been transcribed for various instruments, including piano, harpsichord, and orchestra. BWV 564 remains a popular and frequently performed work in the organ repertoire.