 There, she sang Sophie in the first Berlin performance of Richard Strauss' "Der Rosenkavalier", which impressed Thomas Beecham so much that he invited her to sing that role at the opera's first performance in London at the Royal Opera House in 1913.Dux had made her London debut in 1911 with Thomas Beecham at His Majesty's Theatre.During the years from 1918 until 1921, Dux sang mostly in concert recitals and toured the Royal Swedish Opera in Stockholm.