Beethoven composed his Clarinet Trios op. 11 and 38 in 1798 and 1802/03. The op. 11 was given the nickname “Gassenhauer Trio” because its third movement is a set of variations on a theme from Joseph Weigl’s opera L’amor marinaro (“Gassenhauer” means a “popular song”). Playing with many possibilities in these nine variations, Beethoven sometimes lets the piano appear alone, and sometimes has it rest. In places the mood is that of a sort of funeral march, and there are harmonic and rhythmic surpri...