Singers Deborah Polaski (R) and Patricia Petibon perform on stage during a dress rehearsal of Francis Poulenc's opera 'Dialogues des Carmelites' at Theater an der Wien in Vienna April 13, 2011. The opera is conducted by Bertrand de Billy and will premiere on April 16.   REUTERS/Herwig Prammer (AUSTRIA - Tags: ENTERTAINMENT)
RM2CYMKE7Singers Deborah Polaski (R) and Patricia Petibon perform on stage during a dress rehearsal of Francis Poulenc's opera 'Dialogues des Carmelites' at Theater an der Wien in Vienna April 13, 2011. The opera is conducted by Bertrand de Billy and will premiere on April 16. REUTERS/Herwig Prammer (AUSTRIA - Tags: ENTERTAINMENT)
Singers Deborah Polaski (R) and Patricia Petibon perform on stage during a dress rehearsal of Francis Poulenc's opera 'Dialogues des Carmelites' at Theater an der Wien in Vienna April 13, 2011. The opera is conducted by Bertrand de Billy and will premiere on April 16.   REUTERS/Herwig Prammer (AUSTRIA - Tags: ENTERTAINMENT SOCIETY)
RM2CYN5ARSingers Deborah Polaski (R) and Patricia Petibon perform on stage during a dress rehearsal of Francis Poulenc's opera 'Dialogues des Carmelites' at Theater an der Wien in Vienna April 13, 2011. The opera is conducted by Bertrand de Billy and will premiere on April 16. REUTERS/Herwig Prammer (AUSTRIA - Tags: ENTERTAINMENT SOCIETY)
Singers Deborah Polaski (L) and Patricia Petibon perform on stage during a dress rehearsal of Francis Poulenc's opera 'Dialogues des Carmelites' at Theater an der Wien in Vienna April 13, 2011. The opera is conducted by Bertrand de Billy and will premiere on April 16.   REUTERS/Herwig Prammer (AUSTRIA - Tags: ENTERTAINMENT SOCIETY)
RM2CYNKTGSingers Deborah Polaski (L) and Patricia Petibon perform on stage during a dress rehearsal of Francis Poulenc's opera 'Dialogues des Carmelites' at Theater an der Wien in Vienna April 13, 2011. The opera is conducted by Bertrand de Billy and will premiere on April 16. REUTERS/Herwig Prammer (AUSTRIA - Tags: ENTERTAINMENT SOCIETY)