When summer comes, the Mostly Mozart Festival isn’t the only game in town, but it’s the biggest. (I am speaking of music here; I have no desire to slight the New York Yankees.) Mostly Mozart is a festival of about four weeks, offering a variety of performances, taking place at a variety of Lincoln Center venues. Administration knows what it’s doing. And staffers go about their work with notable good cheer. A happy feeling pervades this festival, or so it seems to me.

Definitely happy—or happy-appearing—is the music director, Louis Langrée. He seems grateful to be a musician. He may be an awful gloomy Gus behind the scenes—I know nothing about him, personally—but, onstage, he is consistently sunny. He doesn’t so much walk onto the stage as bound onto it, eager and delighted to do business. He conducted the opening concert of 2010, and the orchestra was his, and the festival’s,...