Scooby-Doo! Stage Fright (2013) on Netflix

Plot summary

Fred and Daphne have reached the finals of Talent Star, a talent competition hosted by Brick Pimiento, and the whole gang comes with them to Chicago, where the show is staged in an opera house. On arrival they hear that a Phantom is disrupting the production and openly favors one finalist, Chrissy, to win the prize. They also befriend Emma Gale, a violinist whose parents need the winnings to keep their home out of bankruptcy. Fred, Daphne and Velma set up surveillance cameras to catch the Phantom but cannot, since he seems able to be in several places at once. The gang divides to look for clues, and Fred and Daphne meet the opera house owner Mel Richmond, who says a Phantom terrorized the building thirty-five years ago.