Twitter launched its new #Music app to the public on Thursday. The service allows you to preview what songs are popular based on who is talking about them. If you're signed in to Twitter, #music will customize a list based on artists that you already follow and will also recommend new songs to listen to. If you sign in with a Spotify or Rdio accound, you will be able to listen to full tracks. This could be a great way to discover new music, and, of course, it's also a great way for Twitter to get people to spend more time on Twitter.