“A queen reigns in Vienna,” by Paul du Quenoy

“A queen reigns in Vienna,” by Paul du Quenoy

“Who does Crimea belong to?” asked a Ukrainian-language sign held by a protestor outside the Vienna State Opera on a balmy June evening. Moments later, despite a small demonstration that diffident Viennese passersby and members of the sold-out audience seemed content to ignore, the superstar soprano Anna Netrebko made her much-anticipated debut in one of the Russian repertoire’s most challenging dramatic soprano roles, Liza, in Tchaikovsky’s pen…