Singers Nadia Krasteva (L) and Tamar Iveri perform on stage as Olga and Tatjana during a dress rehearsal of Pyotr Illyich Tchaikovsky's opera Eugene Onegin at Vienna's State Opera March 3, 2009. The opera, conducted by Maestro Seiji Ozawa and directed by Falk Richter, will premiere on March 7. REUTERS/Herwig Prammer (AUSTRIA) 

Singers Nadia Krasteva and Ramon Vargas (L-R) perform on stage as Olga and Lenski during a dress rehearsal of Pyotr Illyich Tchaikovsky's opera Eugene Onegin at Vienna's State Opera March 3, 2009. The opera, conducted by Maestro Seiji Ozawa and directed by Falk Richter, will premiere on March 7. REUTERS/Herwig Prammer (AUSTRIA) 

Singers Simon Keenlyside, Nadia Krasteva and Ramon Vargas (L-R) perform on stage as Eugene Onegin, Olga and Lenski during a dress rehearsal of Pyotr Illyich Tchaikovsky's opera Eugene Onegin at Vienna's State Opera March 3, 2009. The opera, conducted by Maestro Seiji Ozawa and directed by Falk Richter, and will premiere on March 7. REUTERS/Herwig Prammer (AUSTRIA) 

Singer Nadia Krasteva (C) performs as Preziosilla during a dress rehearsal of Giuseppe Verdi's opera "La forza del destino" on stage of Vienna's opera house February 26, 2008. The opera is conducted by Maestro Zubin Mehta, directed by David Pountney, and will have its premiere on March 1. REUTERS/Herwig Prammer (AUSTRIA) 

Singer Nadia Krasteva performs as Preziosilla during a dress rehearsal of Giuseppe Verdi's opera "La forza del destino" on stage of Vienna's opera house February 26, 2008. The opera is conducted by Maestro Zubin Mehta, directed by David Pountney, and will have its premiere on March 1. REUTERS/Herwig Prammer (AUSTRIA) 

Singers Carlos Alvarez (L) and Nadia Krasteva performs as Don Carlos and Preziosilla during a dress rehearsal of Giuseppe Verdi's opera "La forza del destino" on stage of Vienna's opera house February 26, 2008. The opera is conducted by Maestro Zubin Mehta, directed by David Pountney, and will have its premiere on March 1. REUTERS/Herwig Prammer (AUSTRIA) 

Singer Nadia Krasteva (C) performs as Preziosilla during a dress rehearsal of Giuseppe Verdi's opera "La forza del destino" on stage of Vienna's opera house February 26, 2008. The opera is conducted by Maestro Zubin Mehta, directed by David Pountney, and will have its premiere on March 1. REUTERS/Herwig Prammer (AUSTRIA) 

Singers Nadia Krasteva (centre R top) and Martina Serafin (centre R) perform on stage during a dress rehearsal of Peter Ilyich Tchaikovsky's opera "Pique Dame" at the State Opera in Vienna October 23, 2007. The opera is conducted by Maestro Seiji Ozawa and will have its premiere on October 28. REUTERS/Herwig Prammer (AUSTRIA) 

Singers Nadia Krasteva, Martina Serafin and Aura Twarowska (L-R) perform on stage during a dress rehearsal of Peter Ilyich Tchaikovsky's opera "Pique Dame" at the State Opera in Vienna October 23, 2007. The opera is conducted by Maestro Seiji Ozawa and will have its premiere on October 28. REUTERS/Herwig Prammer (AUSTRIA) 

Bulgarian singer Nadia Krasteva performs on stage during a dress rehearsal of Modest Mussorgsky's opera "Boris Godunov" as Marina Mnischek at Vienna's State Opera May 24, 2007. The opera is conducted by Daniele Gatti of Italy and will have its premiere on May 28. REUTERS/Herwig Prammer (AUSTRIA) 

Bulgarian singer Nadia Krasteva (R) and Marian Talaba of Ukraine perform on stage during a dress rehearsal of Modest Mussorgsky's opera "Boris Godunov" as Marina and Grigori at Vienna's State Opera May 24, 2007. The opera is conducted by Daniele Gatti of Italy and will have its premiere on May 28. REUTERS/Herwig Prammer (AUSTRIA) 

Bulgarian singer Nadia Krasteva (R) and Marian Talaba of Ukraine perform on stage during a dress rehearsal of Modest Mussorgsky's opera "Boris Godunov" as Marina and Grigori at Vienna's State Opera May 24, 2007. The opera is conducted by Daniele Gatti of Italy and will have its premiere on May 28. REUTERS/Herwig Prammer (AUSTRIA) 

Bulgarian singer Nadia Krasteva (L) and German singer Falk Struckmann perform on stage during a dress rehearsal of Modest Mussorgsky's opera "Boris Godunov" as Marina Mnischek and Rangoni at Vienna's State Opera May 24, 2007. The opera is conducted by Daniele Gatti of Italy and will have its premiere on May 28. REUTERS/Herwig Prammer (AUSTRIA) 

Krassimira Stoyanova (3rd R) performs as "Desdemona" and Nadia Krasteva (4th R) as "Emilia" during a dress rehearsal of Guiseppe Verdi's "Otello" in Vienna's state opera October 20, 2006. REUTERS/Herbert Neubauer (AUSTRIA)