Frederick [the Great], who enjoyed humiliatating [sic] his guests, had composed a long melody line full of chromatic scales that was impossible to turn into a multi-voiced canon (that is, a “round”: think “Row, Row, Row Your Boat” with different groups starting at different times) and told Bach to turn it into a fugue (an even more complicated “round”). Whereupon Bach, on the spot, sat down at one of the new piano fortes and turned it into a three-part fugue. The flummoxed King said, in effect, OK, turn it into a 6-part fugue. A few days later, Bach sent him a 6-part fugue and more than a fugue, “A Musical Offering” that rebuked Frederick and all of his Enlightenment notions with the Christian faith.