George Szell
Some of Melchior's most notable colleagues in the opera houses of the world included the sopranos Frida Leider, Kirsten Flagstad, Lotte Lehmann, Helen Traubel, Marjorie Lawrence, and Elisabeth Rethberg, and conductors Felix Weingartner, Bruno Walter, Wilhelm Furtwängler, Fritz Reiner, Sir Thomas Beecham, Arturo Toscanini, Erich Leinsdorf, George Szell, and Otto Klemperer.