Patti Smith, Elvis Costello, Marcus Mumford and more celebrate Coen brothers' upcoming folkie film. At New York City's Town Hall on Sunday night, Patti Smith had the best line of the night. Glancing at a chorus line of musicians behind her, Smith admitted, "I don't even know who they are, half of them." The audience laughed, and Smith courteously added, "But I'm pleased to see them." With that, Smith and her semi-mystery guests – which included her son Jackson and members of the Avett Brothers and the progressive bluegrass band the Punch Brothers – launched into a stomping, hootenanny makeover of her modern-day empowerment song, "People Have the Power."