The other important change was the introduction of community licenses, which were first issued in 2005 to counter the influence of pirates, and which allow stations to broadcast legally within small radiuses.

Sarah Lockhart, the chief executive and co-founder of Rinse FM, liked the rooftop views that came with being a pirate. But that was the only fun part of being a criminal, she said in an interview at the spotless (though gently pot-scented) East London studio that Rinse FM now occupies. Before it went legal in 2010, Rinse was one of Britain’s most notable pirate stations, transmitting grime, dubstep, and other underground genres. Ms. Lockhart said she hated it. “You couldn’t have a party, you couldn’t do a sponsorship,” she said. “You can get arrested. You can go to jail.”

So when she heard that the communications regulator might be open to pirates transitioning to become legal stations, she jumped on the opportunity. It took her five years to win one of the few community FM spots. Now that Rinse is a licensed station, the contrast with Kool, a former competitor, is stark. Kool operates out of a grim warehouse with flickering bulbs and patchy black paint, but Rinse has leather couches, its own record label, and corporate partners like Smirnoff.

At the same time, Rinse and its contemporaries are hoping to do what the pirates did best: give young people without money or connections space to make new kinds of music.