Since their release in 1978, hit albums like Bruce Springsteen’s “Darkness on the Edge of Town,” Billy Joel’s “52nd Street,” the Doobie Brothers’ “Minute by Minute,” Kenny Rogers’s “Gambler” and Funkadelic’s “One Nation Under a Groove” have generated tens of millions of dollars for record companies. But thanks to a little-noted provision in United States copyright law, those artists — and thousands more — now have the right to reclaim ownership of their recordings, potentially leaving the labels out in the cold.