After establishing itself as a hotbed for bands looking to promote their music, MySpace will today take a significant leap toward generating revenue from the millions of songs it hosts online by partnering with the four major labels, a publisher and an indie music aggregator.

Viewed as the major labels’ first significant step toward cutting into Apple iTunes’ market share in the digital marketplace, MySpace Music will offer expanded catalogs of premium audio and video content, e-commerce wares, user and artist playlists and opportunities for advertisers and sponsors to integrate music into their paid-for messages.

MySpace Music, which is owned by News Corp. and operates within the Fox Interactive unit, has inked as joint venture partners EMI Music, Sony BMG, Universal Music Group, Warner Music Group, Sony/ATV Music Publishing and the Orchard.

Among the offerings expected to be available today are free and unlimited full-length audio streaming, discography and content catalogs for Sony BMG, UMG and WMG artists; DRM-free MP3 downloads for sale through Amazon MP3; and ringtones powered by Jamster. EMI was the last to come aboard, and the tracks it will offer for sale will be added later; Universal Music will discontinue its practice of limiting streams of its artists’ music to 90 seconds.

MySpace Music will launch with several hundred thousand songs with the goal of eventually topping the 8.5 million available on iTunes.

Since it hit critical mass in 2004, MySpace has offered promotional space in which acts can stream music and/or offer videos. New setup adds e-commerce opportunities in addition to more elements that allow personal filtering of the musical offerings.

The first phase employs a toolset that allows members of the MySpace Music community in the U.S. to download, stream and personalize their music content. It allows MySpace users to create playlists for personal and public consumption and allows visitors to stream playlisted content on-demand and purchase MP3s of songs. Search capabilities on the site have also been greatly enhanced.

One of the more interesting propositions from MySpace is the integration of advertisers’ products within musical offerings. Beginning today, for example, Sony Pictures will wrap the site’s music players in ads for “Nick & Norah’s Infinite Playlist” for a week. McDonald’s and Toyota will give away music downloads; “Toyota Tuesdays” will feature a different free download over the next 52 weeks.

From the major labels’ perspective, it is likely that MySpace will play a significantly increased role in the digital strategy for new releases. In informal discussions with industry executives who have seen demonstrations, there are high hopes for a playlist function in which users can share the titles of songs, which in turn could generate sales. For MySpace, the service gives it a leg up on rival Facebook, which recently surpassed MySpace in numbers of users.

Down the road, it is believed that MySpace Music will offer ticketing and merchandise sales opportunities for labels and artists.

MySpace had been extremely cagey about announcing any details related to the operation including a launch date. Billboards announcing the service have popped up in the last two weeks, with artists such as the Jonas Brothers, M.I.A. and Lil Wayne touting their favorite songs by other artists.

The service is being launched without a CEO to head the division. After a fruitless six-month search, many in the industry expect Andy Schuon, the former CEO of Universal Music Group’s Intl. Music Feed, to be named head of the company soon.

More than 5 million artists have MySpace pages, and the website boasts 76 million unique visitors per month in the U.S. MySpace has long been a music-driven site; nearly two-thirds of all pages have music on them, and about 6 billion tunes are played every month.

MySpace was one of the first Internet purchases made by News Corp., which paid $580 million for the social networking site in July 2005.