Bach is the irreducible indispens­able of classical music. You would be hard pressed to find a performer who would admit to disliking him; and composers don’t use him — as Benjamin Britten used Beethoven and Brahms and Strauss, for example — to define a contrary aesthetic agenda. He is, as much as a dead white male can be, universal; and also, in a sense, pure. Concert pianists who spend a lot of their time with the Romantic longings which dominate the piano repertoire, from late Mozart to Rachmaninov, have been known to cleanse themselves with an icy immersion in the Bach keyboard works first thing in the morning.