Wolfgang Sawallisch, Marie-Claire Alain, Van Cliburn, and two oboists: William Bennet of the SF Symphony, who had collapsed at a concert while playing Strauss's Oboe Concerto, and Washington McClain, who had played with Tafelmusik.
I don't know if Sawallisch ever conducted Mahler, but his Brahms symphony set with the Vienna Symphony (not the Phil) is excellent. His Hindemith and Strauss from Philadelphia are outstanding.
I still have some of the vinyl LPs on MHS of Ms. Alain's first of three traversals of Bach organ music, and I was privileged to hear her in recital here in Chicago a few years ago.