After a few weeks of speculation, MySpace Music finally launched today, offering users the opportunity to stream full songs for free, build playlists and buy DRM-free tracks from Amazon or ringtones from Jamster. The initiative is part of a joint venture with all four major music companies to counter iTunes and play a key role in the evolution of the music industry, which has suffered from declining CD sales and continued piracy.

Most of the revenue for MySpace Music will come from advertising. And since all four major music labels together own a 40 percent stake in the venture, they stand to gain financially if it attracts enough users. The site will also offer concert ticket purchases and other merchandise.

Music has traditionally been one of the strongest attractions of MySpace, but until now there were few ways for artists to sell their songs on the site. Whether or not this new effort will help the labels downplay Apple's influence in the market is debatable, but at least they are launching with the potential to reach a very broad audience - there are 120 million unique users every month on MySpace.