J.S. Bach Fuga F-Dur BWV 540
Despite all the arguments there is still no proof that the Toccata and the Fugue do or do not belong together. They are thought to be written in different periods. Bach often put pieces together that were not written as one. It is a double fugue, Bach's only through-going one, and not well-known.
As in the Toccata, there are many Italian influences.