The Philadelphia Orchestra matters, and, therefore, it matters who the music director of the Philadelphia Orchestra is. Why does the orchestra matter? Well, it does to me, maybe I should say—and to Philadelphians, and to some others in the world. It has been a leading orchestra for a long time. A special orchestra too, given its sound. Also given its pedigree. For almost seventy years—1912 to 1980—it had exactly two music directors, Stokowski and Ormandy. The latter served forty-four years. Since 1980, the Philadelphians—the “Fabulous Philadelphians,” we used to call them—have had a handful of music directors.

The latest is Yannick Nézet-Séguin, who took over this season. He’s Canadian—French Canadian, obviously—and young, for a conductor: not yet forty. The world is enthusiastic for young conductors now. It used to be that age and experience were venerated. In an...