[2] Alsen debuted as Rocco in Fidelio in Westfalen.
In 1936, he performed as the Commendatore in Mozart's Don Giovanni under Bruno Walter, and as Pogner the goldsmith in Wagner's Die Meistersinger von Nürnberg under Arturo Toscanini.
Basing his career in Vienna, he went on to play all the great Wagner bass roles, including Gurnemanz, Hunding, Fafner, King Marke and Hagen, and more than forty roles by other composers.
Recordings are available of his Hunding, Pogner, and Fafner; also Rocco, Banco, Commendatore (opposite Ezio Pinza), Sarastro, and Osmin (opposite Elisabeth Schwarzkopf).
This article about a German opera singer is a stub.