Opera cast member Anna Netrebko acknowledges the applause at the end of the season opening of La Scala theatre in Milan, Italy December 7, 2019. REUTERS/Alessandro Garofalo 

Opera cast member Anna Netrebko acknowledges the applause at the end of the season opening of La Scala theatre in Milan, Italy December 7, 2019. REUTERS/Alessandro Garofalo 

Opera singer Anna Netrebko reacts during the opening ceremony of the traditional Opera Ball in Vienna, Austria February 28, 2019. REUTERS/Leonhard Foeger 

Opera singers Anna Netrebko and Yusif Eyvazov perform during the opening ceremony of the traditional Opera Ball in Vienna, Austria February 28, 2019. REUTERS/Leonhard Foeger 

Opera singer Anna Netrebko performs during the opening ceremony of the traditional Opera Ball in Vienna, Austria February 28, 2019. REUTERS/Leonhard Foeger 

Opera singer Anna Netrebko performs during the opening ceremony of the traditional Opera Ball in Vienna, Austria February 28, 2019. REUTERS/Leonhard Foeger 

Opera singer Anna Netrebko performs during the opening ceremony of the traditional Opera Ball in Vienna, Austria February 28, 2019. REUTERS/Leonhard Foeger 

Opera singer Anna Netrebko performs during the opening ceremony of the traditional Opera Ball in Vienna, Austria February 28, 2019. REUTERS/Leonhard Foeger 

Opera singer Anna Netrebko gestures during the opening ceremony of the traditional Opera Ball in Vienna, Austria February 28, 2019. REUTERS/Leonhard Foeger 

Opera singer Anna Netrebko performs during a dress rehearsal for the traditional Opera Ball in Vienna, Austria February 27, 2019. REUTERS/Leonhard Foeger 

Opera singer Anna Netrebko performs during a dress rehearsal for the traditional Opera Ball in Vienna, Austria February 27, 2019. REUTERS/Leonhard Foeger 

Opera singer Anna Netrebko performs during a dress rehearsal for the traditional Opera Ball in Vienna, Austria February 27, 2019. REUTERS/Leonhard Foeger 

Opera singers Anna Netrebko and Yusif Eyvazov perform during a dress rehearsal for the traditional Opera Ball in Vienna, Austria February 27, 2019. REUTERS/Leonhard Foeger 

Opera singer Anna Netrebko performs during a dress rehearsal for the traditional Opera Ball in Vienna, Austria February 27, 2019. REUTERS/Leonhard Foeger 

Opera singer Anna Netrebko performs during a dress rehearsal for the traditional Opera Ball in Vienna, Austria February 27, 2019. REUTERS/Leonhard Foeger 

Opera singer Anna Netrebko performs during a dress rehearsal for the traditional Opera Ball in Vienna, Austria February 27, 2019. REUTERS/Leonhard Foeger 

People watch a live broadcast of the sold-out Staatsoper premiere of Verdis "Macbeth" with Placido Domingo in the title role and Anna Netrebko as Lady Macbeth as part of the Staatsoper für alle ("State Opera for Everyone") annual classical concerts at Bebelplatz in Berlin, Germany, June 17, 2018, the same time as Germany plays Mexico during the World Cup in Russia. REUTERS/Hannibal Hanschke 

People watch a live broadcast of the sold-out Staatsoper premiere of Verdis "Macbeth" with Placido Domingo in the title role and Anna Netrebko as Lady Macbeth as part of the Staatsoper für alle ("State Opera for Everyone") annual classical concerts at Bebelplatz in Berlin, Germany, June 17, 2018, the same time as Germany plays Mexico during the World Cup in Russia. REUTERS/Hannibal Hanschke 

People watch a live broadcast of the sold-out Staatsoper premiere of Verdis "Macbeth" with Placido Domingo in the title role and Anna Netrebko as Lady Macbeth as part of the Staatsoper für alle ("State Opera for Everyone") annual classical concerts at Bebelplatz in Berlin, Germany, June 17, 2018, the same time as Germany plays Mexico during the World Cup in Russia. REUTERS/Hannibal Hanschke 

Russian-Austrian soprano singer Anna Netrebko and the Vienna Philharmonic Orchestra perform on stage during the Summer Night Concert in front of Schoenbrunn Palace in Vienna, Austria, May 31, 2018. REUTERS/Lisi Niesner 

Russian-Austrian soprano singer Anna Netrebko, Russian conductor Valery Gergiev and the Vienna Philharmonic Orchestra perform on stage during the Summer Night Concert in front of Schoenbrunn Palace in Vienna, Austria, May 31, 2018. REUTERS/Lisi Niesner 

Russian-Austrian soprano singer Anna Netrebko, Russian conductor Valery Gergiev and the Vienna Philharmonic Orchestra perform on stage during the Summer Night Concert in front of Schoenbrunn Palace in Vienna, Austria, May 31, 2018. REUTERS/Lisi Niesner 

Russian-Austrian soprano singer Anna Netrebko and the Vienna Philharmonic Orchestra perform on stage during a dress rehearsal of the Summer Night Concert in front of Schoenbrunn Palace in Vienna, Austria, May 30, 2018. REUTERS/Lisi Niesner 

Russian-Austrian soprano singer Anna Netrebko and the Vienna Philharmonic Orchestra perform on stage during a dress rehearsal of the Summer Night Concert in front of Schoenbrunn Palace in Vienna, Austria, May 30, 2018. REUTERS/Lisi Niesner 

Russian-Austrian soprano singer Anna Netrebko poses for photographers ahead of a news conference in Vienna, Austria, May 30, 2018. REUTERS/Lisi Niesner 

Russian-Austrian soprano singer Anna Netrebko poses for photographers ahead of a news conference in Vienna, Austria, May 30, 2018. REUTERS/Lisi Niesner 

Russian-Austrian soprano singer Anna Netrebko attends a news conference in Vienna, Austria, May 30, 2018. REUTERS/Lisi Niesner 

Russian-Austrian soprano singer Anna Netrebko poses for photographers ahead of a news conference in Vienna, Austria, May 30, 2018. REUTERS/Lisi Niesner 

Russian-Austrian soprano singer Anna Netrebko attends a news conference in Vienna, Austria, May 30, 2018. REUTERS/Lisi Niesner 

Russian-Austrian soprano singer Anna Netrebko attends a news conference in Vienna, Austria, May 30, 2018. REUTERS/Lisi Niesner 

Tenor Yusif Eyvazov, director Riccardo Chailly and soprano Anna Netrebko acknowledge the applause at the end of the "Andrea Chenier" by Umberto Giordano which opened the 2017-18 season at Milan's La Scala opera house, Italy December 7, 2017. REUTERS/Stefano Rellandini 

Tenor Yusif Eyvazov (L), director Riccardo Chailly (2L), soprano Anna Netrebko and baritone Luca Salsi acknowledge the applause of the audience at the end of "Andrea Chenier" at La Scala opera house downtown Milan, Italy December 7, 2017. REUTERS/Stefano Rellandini 

Russian soprano Anna Netrebko (C) and the cast acknowledges the applause at the end of the Verdi's Joan of Arc, opening of the 2015-16 opera season at Milan's La Scala opera house, December 7, 2015. REUTERS/Alessandro Garofalo 

Russian soprano Anna Netrebko acknowledges the applause at the end of the Verdi's Joan of Arc, opening of the 2015-16 opera season at Milan's La Scala opera house, December 7, 2015. REUTERS/ Alessandro Garofalo 

Opera singers Anna Netrebko and Yusif Eyvazov arrive for the opening ceremony of the 23rd Life Ball in Vienna, Austria May 16, 2015. Life Ball is Europe's largest annual AIDS charity event and takes place in Vienna's city hall. REUTERS/Leonhard Foeger 

Opera singer Anna Netrebko reacts during a concert at Bellas Artes museum in Mexico City, February 25, 2015. REUTERS/Edgard Garrido (MEXICO - Tags: ENTERTAINMENT ) 

Opera singer Anna Netrebko sings during a concert at Bellas Artes museum in Mexico City, February 25, 2015. REUTERS/Edgard Garrido (MEXICO - Tags: ENTERTAINMENT) 

Opera singers Anna Netrebko and Yusif Eyvazov dance during a concert at Bellas Artes museum in Mexico City, February 25,2015. REUTERS/Edgard Garrido (MEXICO - Tags: ENTERTAINMENT) 

Opera singer Anna Netrebko smiles during a concert at Bellas Artes museum in Mexico City, February 25,2015. REUTERS/Edgard Garrido (MEXICO - Tags: ENTERTAINMENT) 

Opera singer Anna Netrebko sings during a concert at Bellas Artes museum in Mexico City, February 25,2015. REUTERS/Edgard Garrido (MEXICO - Tags: ENTERTAINMENT ) 

Opera singer Anna Netrebko smiles during a concert at Bellas Artes museum in Mexico City, February 25,2015. REUTERS/Edgard Garrido (MEXICO - Tags: ENTERTAINMENT ) 

Opera singer Anna Netrebko gestures during a concert at Bellas Artes museum in Mexico City, February 25, 2015. REUTERS/Edgard Garrido (MEXICO - Tags: ENTERTAINMENT) 

Yevgeny Denisenko, director general of the Donetsk Opera Theatre, displays a certificate of 1 million roubles donated by opera singer Anna Netrebko to the opera and ballet theatre in Donetsk, December 15, 2014. Russian soprano Anna Netrebko, one of the biggest names in international opera, showed her support for the people of Donetsk by donating 1 million rubles ($16,745) to the theatre. REUTERS/Alexander Ermochenko (UKRAINE - Tags: ENTERTAINMENT POLITICS CIVIL UNREST) 

Actors of the Donbass Opera Theatre, also known as the Donetsk Opera Theatre, stage a performance in Donetsk December 13, 2014. Russian soprano Anna Netrebko, one of the biggest names in international opera, has stirred controversy by posing with the flag of Ukraine's pro-Russian rebels and making a donation to the opera house in the separatists' main stronghold, Donetsk. Netrebko said on Facebook she had not recognized the flag of "Novorossiya" (New Russia) when she posed alongside a rebel official on Sunday and entrusted him with the donation of 1 million roubles ($18,439). REUTERS/Maxim Shemetov (UKRAINE - Tags: SOCIETY CIVIL UNREST POLITICS) 

Actors of Donbass Opera Theatre, also known as the Donetsk Opera Theatre, stage a performance in Donetsk December 13, 2014. Russian soprano Anna Netrebko, one of the biggest names in international opera, has stirred controversy by posing with the flag of Ukraine's pro-Russian rebels and making a donation to the opera house in the separatists' main stronghold, Donetsk. Netrebko said on Facebook she had not recognized the flag of "Novorossiya" (New Russia) when she posed alongside a rebel official on Sunday and entrusted him with the donation of 1 million roubles ($18,439). REUTERS/Maxim Shemetov (UKRAINE - Tags: SOCIETY POLITICS CIVIL UNREST) 

Actors and employees of Donbass Opera Theatre, also known as the Donetsk Opera Theatre, watch a performance from backstage in Donetsk December 13, 2014. Russian soprano Anna Netrebko, one of the biggest names in international opera, has stirred controversy by posing with the flag of Ukraine's pro-Russian rebels and making a donation to the opera house in the separatists' main stronghold, Donetsk. Netrebko said on Facebook she had not recognized the flag of "Novorossiya" (New Russia) when she posed alongside a rebel official on Sunday and entrusted him with the donation of 1 million roubles ($18,439). REUTERS/Maxim Shemetov (UKRAINE - Tags: SOCIETY CIVIL UNREST POLITICS) 

Musicians of Donbass Opera Theatre orchestra, also known as the Donetsk Opera Theatre, prepare for a performance in Donetsk December 13, 2014. Russian soprano Anna Netrebko, one of the biggest names in international opera, has stirred controversy by posing with the flag of Ukraine's pro-Russian rebels and making a donation to the opera house in the separatists' main stronghold, Donetsk. Netrebko said on Facebook she had not recognized the flag of "Novorossiya" (New Russia) when she posed alongside a rebel official on Sunday and entrusted him with the donation of 1 million roubles ($18,439). REUTERS/Maxim Shemetov (UKRAINE - Tags: SOCIETY CIVIL UNREST POLITICS) 

A violinist of Donbass Opera Theatre orchestra, also known as the Donetsk Opera Theatre, Dmitry Gorshkov prepares for a performance in Donetsk December 13, 2014. Russian soprano Anna Netrebko, one of the biggest names in international opera, has stirred controversy by posing with the flag of Ukraine's pro-Russian rebels and making a donation to the opera house in the separatists' main stronghold, Donetsk. Netrebko said on Facebook she had not recognized the flag of "Novorossiya" (New Russia) when she posed alongside a rebel official on Sunday and entrusted him with the donation of 1 million roubles ($18,439). REUTERS/Maxim Shemetov (UKRAINE - Tags: SOCIETY CIVIL UNREST POLITICS) 

Singers of the Donbass Opera Theatre chorus, also known as the Donetsk Opera Theatre, prepare for a performance in Donetsk December 13, 2014. Russian soprano Anna Netrebko, one of the biggest names in international opera, has stirred controversy by posing with the flag of Ukraine's pro-Russian rebels and making a donation to the opera house in the separatists' main stronghold, Donetsk. Netrebko said on Facebook she had not recognized the flag of "Novorossiya" (New Russia) when she posed alongside a rebel official on Sunday and entrusted him with the donation of 1 million roubles ($18,439). REUTERS/Maxim Shemetov (UKRAINE - Tags: SOCIETY CIVIL UNREST POLITICS) 

Opera singers Anna Netrebko (L) and Placido Domingo play the parts of Leonora and Il Conte di Luna respectively, during a dress rehearsal of Giuseppe Verdi's "Il trovatore" (The Troubadour) in Salzburg August 4, 2014. The opera will premiere as part of the annual Salzburg Festival (Salzburger Festspiele) on August 9. The Salzburg Festival, one of the biggest cultural festivals worldwide, takes place from July 27 to August 31, 2014. More than 270 performances in the genres of opera, drama and concert are scheduled at 16 performance venues in Salzburg during the festival. REUTERS/Heinz-Peter Bader (AUSTRIA - Tags: ENTERTAINMENT SOCIETY) 

Opera singer Anna Netrebko performs as Leonora during a dress rehearsal of Giuseppe Verdi's "Il trovatore" (The Troubadour) in Salzburg August 4, 2014. The opera will premiere as part of the annual Salzburg Festival (Salzburger Festspiele) on August 9. The Salzburg Festival, one of the biggest cultural festivals worldwide, takes place from July 27 to August 31, 2014. More than 270 performances in the genres of opera, drama and concert are scheduled at 16 performance venues in Salzburg during the festival. REUTERS/Heinz-Peter Bader (AUSTRIA - Tags: ENTERTAINMENT SOCIETY) 

Opera singers Francesco Meli (top), who plays the part of Manrico, and Anna Netrebko, who plays the part of Leonora, perform during a dress rehearsal of Giuseppe Verdi's "Il trovatore" (The Troubadour) in Salzburg August 4, 2014. The opera will premiere as part of the annual Salzburg Festival (Salzburger Festspiele) on August 9. The Salzburg Festival, one of the biggest cultural festivals worldwide, takes place from July 27 to August 31, 2014. More than 270 performances in the genres of opera, drama and concert are scheduled at 16 performance venues in Salzburg during the festival. REUTERS/Heinz-Peter Bader (AUSTRIA - Tags: ENTERTAINMENT SOCIETY) 

Opera singers Anna Netrebko (L), who plays the part of Leonora, and Placido Domingo, who plays the part of Il Conte di Luna, perform during a dress rehearsal of Giuseppe Verdi's "Il trovatore" (The Troubadour) in Salzburg August 4, 2014. The opera will premiere as part of the annual Salzburg Festival (Salzburger Festspiele) on August 9. The Salzburg Festival, one of the biggest cultural festivals worldwide, takes place from July 27 to August 31, 2014. More than 270 performances in the genres of opera, drama and concert are scheduled at 16 performance venues in Salzburg during the festival. REUTERS/Heinz-Peter Bader (AUSTRIA - Tags: ENTERTAINMENT SOCIETY) 

(L-R) Opera singers Placido Domingo, who plays the part of Il Conte di Luna, Anna Netrebko, who plays the part of Leonora, and Francesco Meli, who plays the part of Manrico, perform during a dress rehearsal of Giuseppe Verdi's "Il trovatore" (The Troubadour) in Salzburg August 4, 2014. The opera will premiere as part of the annual Salzburg Festival (Salzburger Festspiele) on August 9. The Salzburg Festival, one of the biggest cultural festivals worldwide, takes place from July 27 to August 31, 2014. More than 270 performances in the genres of opera, drama and concert are scheduled at 16 performance venues in Salzburg during the festival. REUTERS/Heinz-Peter Bader (AUSTRIA - Tags: ENTERTAINMENT SOCIETY) 

Opera singer Anna Netrebko performs as Leonora during a dress rehearsal of Giuseppe Verdi's "Il trovatore" (The Troubadour) in Salzburg August 4, 2014. The opera will premiere as part of the annual Salzburg Festival (Salzburger Festspiele) on August 9. The Salzburg Festival, one of the biggest cultural festivals worldwide, takes place from July 27 to August 31, 2014. More than 270 performances in the genres of opera, drama and concert are scheduled at 16 performance venues in Salzburg during the festival. REUTERS/Heinz-Peter Bader (AUSTRIA - Tags: ENTERTAINMENT SOCIETY) 

Opera singers Anna Netrebko (R) and Placido Domingo play the parts of Leonora and Il Conte di Luna respectively, during a dress rehearsal of Giuseppe Verdi's "Il trovatore" (The Troubadour) in Salzburg August 4, 2014. The opera will premiere as part of the annual Salzburg Festival (Salzburger Festspiele) on August 9. The Salzburg Festival, one of the biggest cultural festivals worldwide, takes place from July 27 to August 31, 2014. More than 270 performances in the genres of opera, drama and concert are scheduled at 16 performance venues in Salzburg during the festival. REUTERS/Heinz-Peter Bader (AUSTRIA - Tags: ENTERTAINMENT SOCIETY) 

Singer Anna Netrebko reacts on stage in front of the Vienna city hall during the opening ceremony of the 22nd Life Ball in Vienna May 31, 2014. Life Ball is Europe's largest annual AIDS charity event and takes place in Vienna's city hall. REUTERS/Leonhard Foeger (AUSTRIA - Tags: ENTERTAINMENT) 

Singer Anna Netrebko performs on stage in front of the Vienna city hall during the opening ceremony of the 22nd Life Ball in Vienna May 31, 2014. Life Ball is Europe's largest annual AIDS charity event and takes place in Vienna's city hall. REUTERS/Leonhard Foeger (AUSTRIA - Tags: SOCIETY ENTERTAINMENT) 

Singers Anna Netrebko (R) and Piotr Beczala perform on stage during a dress rehearsal of Giacomo Puccini's opera "La Boheme" in Salzburg July 28, 2012. The opera is conducted by Daniele Gatti, directed by Damiano Michieletto, and will premiere on August 1 as part of the annual Salzburg Festival. REUTERS/Herwig Prammer (AUSTRIA - Tags: ENTERTAINMENT) 

Singers Anna Netrebko (L) and Piotr Beczala perform on stage during a dress rehearsal of Giacomo Puccini's opera "La Boheme" in Salzburg July 28, 2012. The opera is conducted by Daniele Gatti, directed by Damiano Michieletto, and will premiere on August 1 as part of the annual Salzburg Festival. REUTERS/Herwig Prammer (AUSTRIA - Tags: ENTERTAINMENT)