When, in 2009, the Berlin Philharmonic launched the Digital Concert Hall, a streaming-video platform for its concerts, the orchestra had no particular need to bolster its reputation. For decades, the Philharmonic had reigned as the world-champion musical heavyweight. Established in 1882, it had been led by a procession of luminaries: Hans von Bülow, Arthur Nikisch, Wilhelm Furtwängler, Herbert von Karajan, Claudio Abbado, Simon Rattle. And yet the distinctive Berlin sound—I’ve compared it, over the years, to a Rembrandt interior, a Russian men’s choir, and deep-focus cinematography—has never relied on the elevating powers of any one maestro. Indeed, members of the Philharmonic are more likely to ask whether conductors have risen to their level. Rattle, who departed in 2018, described them as a company made up of leading actors. They are…