The lights dim in Ludlow Garage’s basement theater. A band of shimmering Swedes explodes on stage, dressed like they just beamed down from 1975. The rhythm section builds a bassy four-on-the-floor ...

In many cases throughout the history of rock, pop, and R&B music, cover songs have been afterthoughts, ways for bands to fill out albums or B-sides when they’ve exhausted their supply of originals.