I did not mean running the Webview in a service. Obviously he wants the user to continue to listen to something while his app is paused. The service might be able to play that mp3, stream o.a. (?)
There are ways to find the real stream in Youtube (not the URL that Youtube shows at the top of the sceen, but a much more complicated longer URL), although finding these streams is not so easy. You could probably store that stream (while your app is running) and pass it on to a mediaplayer in the service.