Singers Eva Liebau (L) and Marie-Claude Chappuis perform on stage during a dress rehearsal of Richard Strauss' opera 'Ariadne auf Naxos' in Salzburg July 25, 2012. The opera is conducted by Daniel Harding, directed by Sven-Eric Bechtolf, and will premiere on July 29 as part of the annual Salzburg Festival. REUTERS/Herwig Prammer (AUSTRIA)