News Corp.'s (NYSE:NWS) MySpace is jamming. Rupert Murdoch's favorite ridiculously popular social networking site finally launched its new music site yesterday.

Along with its established collection of 5 million musical artist profile pages, most of them unsigned, MySpace Music now offers free ad-supported streaming of music. All four of the major labels -- from Sony (NYSE:SNE) to Warner Music Group (NYSE:WMG) -- are on board. Indie digital distributor Orchard (NASDAQ:ORCD) is also kicking in its growing music library.

More than just slivers of ad-sharing revenue are at play here. MySpace Music sells digital downloads through Amazon.com (NASDAQ:AMZN) and ringtones through Jamster.

Going with Amazon, instead of market leader Apple (NASDAQ:AAPL), is notable. This is the second big deal that Amazon's MP3 store has announced this week, after the online retailer's pact with Google (NASDAQ:GOOG) to deliver digital downloads to G1 smartphone buyers.

MySpace has been a music hotbed over the past few years, and not just for unsigned artists. R.E.M. gave the site a boost when it launched a new CD on the site several years ago, before it was acquired by News Corp. in 2005. 

This doesn't mean that MySpace can turn its back on garage bands everywhere as it makes its promotional push for the major-label participants. The last thing the site needs is for indie bands with loyal followings to bolt to a new social-networking site. Sooner or later, MySpace will have to let unsigned bands' streaming songs get a piece of the revenue-sharing action, too.

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Longtime Fool contributor Rick Munarriz wonders whether ad-supported music will help or hurt download sales. What do you think? Respond in the comment box below. He does not own shares in any of the companies in this story. He is also part of the Rule Breakers newsletter research team, seeking out tomorrow's ultimate growth stocks a day early. The Fool has a disclosure policy.