The Musical Offering is, inarguably, one of Bach’s most striking works. In 1747, upon a visit to the palace of King Frederick the Great of Prussia, the aging Bach was challenged to improvise on a difficult theme given to him by the king, himself a formidable composer and flutist. On the spot, Bach improvised a complex fugue at the keyboard. Within two months following his visit, Bach completed The Musical Offering, a series of canons, fugues and other pieces based entirely on Frederick’s theme. The piece was immediately printed (unusual for Bach's time) and presented with a dedication to the king.
To get a sense of the complexity of The Musical Offering, consider the first canon, sometimes referred to as a "crab canon." It is to be played forwards by one instrument and backwards by another. (Some call this canon and others in this series “puzzle canons,” since Bach provided us only with hints on how to play them.) There has even been online “chatter” about likening this crab canon to a Möbius strip. Listen and learn more via this blog post on the WFMT website.
I, personally, felt Bach’s presence when I toured the special exhibition, The Worlds of M. C. Escher: Nature, Science, and Imagination, at the North Carolina Museum of Art last month. Escher’s work has been associated with Bach’s. In fact, one of Escher’s lithographs is entitled Crab Canon. Have a look here and you’ll begin to see why.