Shares in Napster Inc. gained more than 3 percent Tuesday as large subscriber growth driven by an acquisition helped the on-line music retailer beat expected quarterly sales.

The Los Angeles company, in a release of data prior to its full earnings report April 24, said sales for the fourth quarter ended March 31 rose almost 5 percent to $28 million.

The company previously forecast quarterly revenue of $26 million. Analysts polled by Thomson Financial anticipate revenue of $26.6 million and a loss of 21 cents per share for the quarter.

Napster cited its acquisition of AOL’s Music Now service last fall, which added 225,000 subscribers to its service. Also boosting sales were a pair of agreements Napster signed earlier this year with AT & T; Inc. and Virgin Group Ltd. to provide music services to some of their mobile customers.

Shares in Napster gained 13 cents, or 3.1 percent, to $4.28 in afternoon trading Tuesday on the Nasdaq.