[2] He made his stage debut in 1948 at the Opernhaus Düsseldorf as Sergeant Moralès in Bizet's Carmen,[2] directed by Gustaf Gründgens.
Imdahl also had a guest contract with the Zürich Opera House, where he appeared in 1955 as Amonasro in Verdi's Aida, later as Count Luna in Il trovatore, Pizarro in Beethoven's Fidelio and Scarpia in Tosca.
[2] Between 1961 and 1970 he appeared regularly at the Vienna State Opera; he made his debut there as Olivier in Capriccio in January 1961.
He performed the roles of Pizarro in 1970, the Speaker in Mozart's Die Zauberflöte, and the music teacher in Ariadne auf Naxos by Richard Strauss.
In addition, a 1963 live recording of Pfitzner's Palestrina from the Bavarian State Opera was released on CD, conducted by Joseph Keilberth, with Imdahl as Giovanni Morone.