After a week of celebrity-only service — which resulted in plenty of early shilling from the Tommy Lees and Mobys of the world — Twitter’s new #music (hashtag intentional) app is now available to the masses. The app makes recommendations according to Twitter trends or the musicians you already follow; full service (as in, listening to an entire song) requires a paid Rdio or Spotify account. The current Most Popular song is, of course, Psy’s “Gentleman,†but only because “Accidental Racist†dropped last week.