Facebook is starting to roll out a new feature that allows you to listen to the same music that your friends on Facebook Chat are listening to. If you see a music note next to one of your friends on Facebook Chat, you can listen to the same music they are using services like Spotify or Rdio. To listen with your friend, hover the mouse above their name and click the “Listen With” button. If you do not want to share what you are listening to, visit the App Settings page after installing the app. [Facebook Blog]

Rdio is an ad-free music subscription service that is available as a website and has iPhone, iPod Touch, iPad, Android, BlackBerry, and Windows Phone applications.

Rdio is a social music service start-up that has raised $17.5 million from new and existing investors. Mangrove Capital Partners has joined as a new investor along with previous investor Janus Friis through investment entities Atomico and Skype. The funding will be used to expand their platform and regions. Warner Brothers Records Chairman and Grammy-nominated producer Rob Cavallo is also joining the board of directors at Rdio.

The entrepreneur dynamic duo Janus Friis with Niklas Zennström has officially launched the Rdio service to the public. You may remember Janus and Niklas as the two who started KaZaa, Skype, and Joost. Up until today, you needed an invitation to use the service. The music streaming service starts at a cost of $4.99 per month. However the service is currently open to users in the U.S. and Canada.

Janus Friis and Niklas Zennström are two of the most popular entrepreneurs as they started KaZaa, Skype, and Joost. Their latest venture is a Twitter-like digital music service called Rdio.com.