Music streaming service Rdio opened to the public on Tuesday with an additional distributor’s content and availability in Canada. It had been in private beta release since early June.

Rdio has added IODA to the content it has already licensed from all four majors as well as IRIS, The Orchard and Finetunes. The company says its catalog is now up to seven million songs. That’s welcome news as the service's relatively thin catalog has been a weak point.

The service offers a social take on listening to and discovering music. Users add friends just as they would at a social networking service. A feed – similar to Facebook’s feed – follows the actions of a user’s social network – which can include organizations with Rdio accounts such as KCRW and Pitchfork. When someone adds an album to a collection, updates a playlist or adds friends, his social network will know.

In addition, Rdio allows a user to quickly scan the most popular albums in his social network (yes, Rdio is an album-based experience). This familiar and intuitive way of sharing and discovering music gives Rdio an important, valuable point of differentiation against its competitors.

Pricing is standard compared to Rdio’s competitors. The basic PC-only streaming service costs $4.99 per month. Use of mobile apps – for iPhone, Android and Blackberry – in addition to PC streaming costs $9.99 per month.

Rdio was founded by Janus Friis and Niklas Zennström, founders of Kazaa and Skype. Its president is Drew Larner, a former managing partner at Europlay Capital Partners and executive vice president at Spyglass Entertainment Group.

Friis will be a featured keynote speaker at Billboard’s Mobile Entertainment Live: The Music App Summit, taking place Oct. 5 at Moscone West in San Francisco. For more information about the conference, please visit