Huntley Dent’s recent review of Bernstein’s Mahler and now his lucid evaluation of several recordings of Tristan und Isolde put me in mind not so much of operatic traditions as those of the concert hall, since Wagner’s music drama is so deeply rooted in the orchestra and the conductor who leads it. The modern symphony orchestra and the concert halls in which they play evolved as a substantially bourgeois institution over the course of the nineteenth century.