The digital music service just introduced apps for iOS and Android devices that will stream music stations tailored to fans of particular performers, songs, and genres or preferences registered by celebrities, social network friends, and users themselves. They won’t offer on-demand music — copyright laws restrict that for a radio-like free service. Users can only skip past unwanted songs six times per station per hour. They also can’t have stations that only play the music of one performer. Still, execs believe they’ll have a leg up on competitors by enabling users to share stations with friends on Rdio, Facebook, or Twitter. In addition, the company says that others can’t match its 2.3M station options. The business model remains a little murky. The new service will be ad-free for now. Execs hope that many users will be so enchanted that they’ll upgrade to the on-demand service which costs $10 a month. Today’s announcement isn’t directly tied to radio giant Cumulus’ recent agreement to buy a major stake in Rdio’s parent, Pulser Media. But Cumulus will sell ads for Rdio’s radio service for Web browsers.