 After Biel-Solothurn, he became Ernest Ansermet's assistant with the Orchestre de la Suisse Romande.Maag was first conductor at the Düsseldorf Opera from 1952 to 1955, and then Generalmusikdirektor of the Bonn City Theater from 1955 to 1959.His first appearance at the Royal Opera House Covent Garden was in 1959, with Mozart's Die Zauberflöte.