As expected, Beats co-founders Iovine and rapper Dr. Dre will join Apple as part of the acquisition of the music streaming and audio equipment company. They should prove key in forging relationships with an industry that historically viewed Apple with suspicion but in recent years has pressed the iPhone maker to do more on subscription services, a market expected to eclipse song downloads in the long run. Iovine’s music industry relationships could ease notoriously difficult licensing negotiations for a future streaming service, recording industry executives say.