Spanish tenor Placido Domingo, 60, is to undergo surgery following acute pain, forcing him to cancel his upcoming performances in Vienna, a statement from the State Opera said Friday. No details of his ailment were reported. The opera star was scheduled to appear in “Pagliacci” starting Monday, but he will now be replaced. Domingo and his doctor are confident that the star will be fit enough to appear in Wagner’s “The Valkyre” beginning May 10, reports the Associated Press. According to Domingo’s Web site, this year he is also expected to act in a feature film based on the life of opera composer Giacomo Puccini (who wrote “Madame Butterfly”).