The plot may sound oddly familiar: Operatic sensation Christina Joseph leaves a promising career at La Scala and returns to her roots in Nashville, Tenn., singing backup at the Country Palace. There she finds an enemy in an aging Country-Western diva and a mentor in a mysterious janitor determined to make her Country Music’s newest star. Basically, Iit’s a splashy Country-Western send-up of the classic tale of horror, “<i>The Phantom Of The Opera</i>. Tickets are $13 for adults, $10 for seniors, $9 for students. Kids 12 and younger get in for $6.