Rdio's latest round of funding, reported by Billboard last week, now has a dollar figure attached to it: $17.5 million, according to a statement from the company.

The new round of funding, from new and existing investors, will be used to help Rdio "aggressively expand its footprint to new platforms and new regions in 2011." Currently the service is available only in the U.S.

In addition, Warner Bros. Records chairman Rob Cavallo has been added to Rdio's board of directors. Cavallo will "help further strengthen Rdio's relationship with the music industry," according to the press release.

Named chairman of Warner Bros. Records in September 2010, Cavallo signed and produced Green Day and Goo Goo Dolls, and has also produced or co-produced albums by Kid Rock, My Chemical Romance, Paramore, Fleetwood Mac and Avril Lavigne.

The addition of a well-connected, high-profile executive like Cavallo is likely to have a positive impact on Rdio's growth: Consumer adoption can be improved when artists are on board, using it and talking about it. Recall that Apple shrewdly involved U2 in the promotion of the iTunes Music Store and the creation of branded products. And before the store's launch, Steve Jobs appealed directly to the Eagles to get them on board.

Rdio differs from other music services in that it places a heavy emphasis on social functions. Like other cloud-based services, Rdio has two price points: a $5-per-month PC-only option and a $10-per-month option that adds access to a mobile app. Rdio's mobile app is available for iPhone/iPod Touch, Android and BlackBerry. Rdio has not released figures on the number of subscribers it has signed up since its launch in August 2010.