What could be the speciality of a genre to which so many different composers connected from Beethoven to Bartók, from Smetana to Kurtág? Is it lightness, brevity, transiency, or ambiguity? The French word bagatelle (trifle, nothing) can mean all of them.

The best bagatelles in the history of music, however, are not superficial at all. Although they grasp the moment, and they are often unpredictable and whimsical, they still contain deep, pithy, and original ideas. The inspiration to compose m...