He appeared with that company through 1938, in Aïda (with Elisabeth Rethberg), Cavalleria rusticana (with Rosa Ponselle), Carmen again (opposite Ponselle), Les contes d'Hoffmann (conducted by Maurice Abravanel and directed by Herbert Graf), Manon (with Bidu Sayão in her Met debut, later with Grace Moore), Faust, and Pagliacci (opposite Robert Weede in his Met debut).
Herbert Hoover | Herbert Kitchener, 1st Earl Kitchener | Herbert von Karajan | Graf | Frank Herbert | Herbert Marcuse | Herbert Read | Herbert Blomstedt | Herbert Grönemeyer | Herbert Beerbohm Tree | Matthew Herbert | Herbert Spencer | Victor Herbert | Steffi Graf | Herbert | Herbert A. Simon | George Herbert | Charles Herbert Best | Herbert Howells | George Herbert, 5th Earl of Carnarvon | Brian Herbert | Aubrey Herbert | Sidney Herbert, 1st Baron Herbert of Lea | Herbert Chapman | Herbert Baumann | Herbert Austin | George Herbert Mead | Herbert Wise | Herbert Gintis | Herbert de Losinga |
In 1953, Siepi debuted at the Salzburg Festival with a legendary production of Don Giovanni conducted by Wilhelm Furtwängler, staged by Herbert Graf, and designed by Clemens Holzmeister.