A pair of New York’s top opera stars due to sing in Japan have canceled their performances following the earthquake, the AP reports. Now, the Metropolitan Opera has to “scour the world” to find replacement singers for soprano Anna Netrebko and tenor Joseph Calleja, even though experts said the trip to Tokyo and Nagoya was safe. “Part of what makes opera such an exciting art form is that it is so unpredictable," said a rep for the Met. "If there were a rationality clause in opera singers' contracts, not many opera singers would perform." (More opera stories.)