(Emmanuel Dunand/AFP/Getty Images)

Amazon Prime members are getting a new perk: The company announced Thursday that it's launching its own streaming music service as part of its premium membership package.

The service, called Prime Music, comes at no extra charge to members of Amazon's Prime service, who pay $99 a year for free two-day shipping and access to the company's video content.

The move gives Amazon a foot in the door of the growing online music world and may help it smooth any ruffled feathers among its valuable Prime customers after it decided to hike the annual cost of Prime membership earlier this year, to $99 from $79.

Prime Music is ad-free and unlimited. Like Spotify, Prime Music will let users pick the specific tracks that they want, rather than having them tune into a Pandora-like radio station featuring songs from a certain genre.  Amazon is also applying its recommendation expertise to the service by suggesting tracks you might like based on the ones you pick yourself and by offering curated playlists  with names like "Feel-Good Country" and "80s Dance Floor Fillers."

Before you get too excited, however, there are a couple of caveats. The main one is that while Amazon's new service does include songs from top artists such as Justin Timberlake, Bruno Mars, Blake Shelton  and Madonna, the online retail giant hasn't struck deals with all the major music labels.

So, the odds are that you'll quickly find that some song you want to listen to -- like any original Beatles song  -- isn't available on the free service. Missing, too, are the hits of the moment. BuzzFeed reported that Amazon won't get access to songs until the tunes have been out for six months. That kind of delay echoes other content deals the company has made, such as its agreement with HBO to include only items from the back catalog in Prime.

Amazon's service isn't going to knock any of its competitors out of the water right away. But that's probably not Amazon's immediate goal. The company has shown in the past that it's happy to release small services that sweeten the deal for Prime customers and grow them over time. For example, Prime Instant Video didn't boast a large variety of content when it launched, but it has become more attractive over time.

The timing of this announcement has also sparked speculation that Amazon may have more music-related news up its sleeve for its mysterious press event set for June 18. The company is widely expected to release a phone at that time -- offering some sort of music and phone bundle could make the rumored device more attractive to consumers.

(Amazon chief executive Jeffrey P. Bezos owns The Washington Post.)

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