By Rick HowlettAbbey Road on the River, billed as the world's largest Beatles-inspired festival, is underway in downtown Louisville.The Beatles tribute band BritBeat helped launch the celebration Thursday afternoon with a free rooftop concert near Fourth Street Live. The festival moved to Louisville from Cleveland several years ago, and is expected to draw 50,000 fans to the Belvedere and surrounding venues through the weekend.In addition to dozens of tribute band peformances, there will be singing competitions, discussion groups, and two film screenings.In the fictional Let Him Be, two young filmmakers explore the possibililty that John Lennon is still alive and living in Canada. The other is a documentary called The Mayor of Strawberry Fieldsabout a homeless man who lives near Lennon's memorial in New York's Central Park.To hear an interview with Peter McNamee, director of Let Him Be, click here.