BBM Music allows BlackBerry users to select 50 songs from a catalog of millions of tracks for their own personal playlist, said Alistair Mitchell, RIM's vice president of BBM platform and integrated services. BBM users can share songs from that list with friends who use the instant messenger service.

Users will pay US$4.99 a month for the BBM Music service. A closed trial run of the service began in Canada, the U.S. and the U.K. Thursday, leading up to a wide release in 18 countries overall later this year. "More than 45 million customers already love the social communication benefits delivered through BBM and we are thrilled to be extending the experience into a uniquely social and interactive music service," said Mike Lazaridis, RIM president and co-CEO.

RIM said music can be saved to smartphones to listen to while offline and users can keep track of how many friends are listening to your tracks. "A major component of online music continues to be about community, and the ability to discover new artists and music through word of mouth," Rob Wells, president of Global Digital Business for Universal Music Group said in a statement.

Some tech blogs came out swinging after RIM made its announcement, making unfavorable comparisons with other music services like Rdio and Spotify, which charge $10 a month but have no song limits.

"RIM Launches Inexplicable BBM Music App," wrote TechCrunch, while Gizmodo headlined its story: "BlackBerry's BBM Music Is The Dumbest Music Service I've Ever Heard Of."