The cycle of fugues is introduced and concluded by a Praeludium and Postludium, the second formed by turning the Praeludium upside down and reading it backwards. In solving technical problems he posed himself, Hindemith created not a dry exercise but a work of considerable imagination. Intellectual achievement and sheer delight in playing are shown not to be mutually exclusive. The Ludus is a graphic example of the composer's delight in the fantastic, offered to his wife, born under the sign of Leo, as a birthday present. He illustrated the work with coloured pencil, among other things drawing a lion for each entry of the subject of the fugues and for each of the twelve a different kind of lion, according to the character of the music, originally published in a limited edition but providing an instructive formal analysis of the music.