[1] Attracted to the stage as a career, he studied singing at the Nuremberg Conservatory, making his debut in that city in 1945 as Tommaso in Eugen d'Albert's Tiefland.
He progressed through the provincial German houses including Hanover (1953–1956) and Frankfurt-am-Main (1956–1959); he joined the Bavarian State Opera in Munich in 1959.
During these years he began to build an international career, not only in the German repertoire but in roles including Bartolo in The Marriage of Figaro, King Philip in Don Carlos, Sparafucile in Rigoletto, Ramphis in Aida, Gremin in Eugene Onegin, and Arkel in Pelléas et Mélisande.
[1][2][3] Other parts in his repertoire included Daland in Der fliegende Holländer, Pogner in Die Meistersinger and Gurnemanz in Parsifal.
[1] Kreppel features in several recordings, including Don Giovanni (conducted by Ferenc Fricsay), Martha (Wilhelm Schuchter), Tristan und Isolde (Horst Stein), Fidelio (Herbert von Karajan), Dalibor (Josef Krips), Der Freischütz (Eugen Jochum), La forza del destino (Dimitri Mitropoulos) and Aida (Lovro von Matačić), but in the view of Kreppel's obituarist in The Times, "the best and the best-known" is his Fasolt in Georg Solti's recording of Das Rheingold,[1][5] made in Vienna in 1958.