We began the year with a crab canon; I had vowed to return to the subject, and here we are.

A crab canon is, simply, a palindromic canon.  Or, to put it differently, a tune that harmonizes with itself backwards.  They’re not necessarily hard to write: you just start from both ends, and meet in the middle.  Some things work in both directions, and some don’t; you submit to those that do, and the canon then grows until you tie a bow in the middle and call it quits.

To my taste, the most satisfying crab canons are the shortest: you can hear the theme flowing back and forth, interweaving with itself, more directly when it’s brief than when it starts to spread out.

Here’s a simple example by Bach, from his prep work for the “Goldberg Variations,” where he was finding out what he could do with the bass line.

And here it is engraved, if you can’t read his handwriting.

And here, too, is one of mine, in the form of a three-part round.  (Click to enlarge.)

(Posted by Doug Skinner.)