Helping back the new MySpace Music are three of the biggest recording companies – Vivendi SA’s Universal Music Group, Sony BMG Music Entertainment and Warner Music Group Corp.

Financial terms of the partnership were not disclosed, but each of the music companies will receive an unspecified equity stake in the new company, said Chris DeWolfe, MySpace co-founder and chief executive.

The fourth-largest music company, EMI Group PLC, is not part of the deal.

DeWolfe said MySpace is in licensing talks with “everyone” but declined to say where discussions stand with EMI, home to artists such as Coldplay and Norah Jones.

MySpace Music, which will roll out gradually in coming months, will enable artists to sell music downloads, concert tickets and merchandise such as T-shirts through their profile pages and to offer ringtones through a unit of MySpace parent News Corp.

“We believe that the Web is becoming increasingly more social,” DeWolfe said during a conference call. “MySpace Music is a new way of experiencing music online that everyone can participate in.”

DeWolfe said some tracks will be sold without copy-protection safeguards but noted that the major labels had committed only to experimenting with offering content in an unrestricted format.

Without the copy protections, the tracks will be compatible with Apple’s iPod music players and could place MySpace in direct competition with existing digital music stores such as Apple’s iTunes, Amazon.com and Napster Inc., analysts said.

“It’s definitely got a lot of potential to it, but how much it really changes the game is yet to be determined,” said Michael Gartenberg, vice president and research director for JupiterResearch. “This is one of those important events in the history of digital music, and it has a lot of potential going forward.”

MySpace might also be looking for ways to maintain its lead on rival social network Facebook, which has been gaining in popularity.