Marcel Dupré: Deux Esquisses Op.41
"The Deux 'Esquisses', or Sketches, were written by Marcel Dupré who was Widor's successor at Saint-Sulpice, and by all accounts a phenomenal organist - some say the most virtuosic organist of the twentieth century. Unsurprisingly then, most of his organ music is extremely difficult to play.
The 'Deux Esquisses' are no exception. The first piece features repeated semiquavers in the right hand, and the second is an exercise in octaves mainly for the hands, although there's a spectacular passage for the pedals in octaves halfway through."