In 1969, Sills sang Zerbinetta in the American premiere (in a concert version) of the 1912 version of Richard Strauss's "Ariadne auf Naxos" with the Boston Symphony. Her performance of the role, especially Zerbinetta's aria, "Grossmächtige Prinzessin", which she sang in the original higher key, won her acclaim. Home video-taped copies circulated among collectors for years afterwards, often commanding large sums on Internet auction sites (the performance was released commercially in 2006, garnering high praise). The second major event of the year was her debut as Pamira in Rossini's "The Siege of Corinth" at La Scala, a success that put her on the cover of "Newsweek".