Rhapsody, which has about 800,000 paying subscribers, isn't saying yet how many more people Napster will add to itsservice, but bulking up its business is critical to compete against Spotify, which has about 10 million subscribers, 2 million of them on paid plans.

"I don't know how much Rhapsody paid, but any time you can acquire paying subscribers, that's a good opportunity if the price is right," said Gartner analyst Mike McGuire.

The deal between Rhapsody and Best Buy was an all-stock deal. A Rhapsody spokeswoman said the company isn't disclosing the value of the minority interest it gave up to Best Buy in exchange for Napster.

Rhapsody, in its various incarnations, has been providing subscription-based digital music streaming for about a decade. That business has been overshadowed in the U.S. by the a la carte purchasing of individual songs and entire albums, primarily from the iTunes Store.

However, the subscription model may be gathering momentum, helped by its success in other media, like the subscription-based streaming of TV shows and movies popularized by Netflix.