[1] During World War II, he was a morse code operator, and simultaneously directed an army band and led a string quartet.
[3] In 1957, he recorded a scene from Wagner's Lohengrin, with the Philharmonia Orchestra in London and the singers Elisabeth Schwarzkopf and Christa Ludwig, under the production of Walter Legge.
He conducted Richard Strauss's Der Rosenkavalier for the Royal Opera, Covent Garden in 1963.
In the meantime, at the Vienna and Salzburg festivals he premiered works such as Frank Martin's oratorio Le Mystere de la Nativité (1960) and Rudolf Wagner-Régeny's The Mines at Falun (1961).
Wallberg inaugurated the Munich Opera Festival in 1962 with a performance of Richard Strauss's Die schweigsame Frau.