Qtrax, a brand from the early days of P2P file-sharing, is poised to relaunch as a legal service.

In a deal with EMI Music the Qtrax service will offer EMI's catalogue to its users.

Consumers will get free music, but Qtrax is now ad-supported and the free songs are in the proprietary 'mpq' format that can only be played a limited number of times on the computer to which they were initially downloaded.

Each time the track is played, the Qtrax player will offer click-to-buy purchasing and suggest that users pay a flat monthly fee to upgrade to a premium subscription service.

This will provide unlimited downloads in Windows Media format which can be transferred to any digital music player except Apple's iPod.

"Qtrax is going to offer the consumer a pretty cool way to sample and discover music in a way that P2P users are used to," said Ken Parks, EMI's senior vice president for strategy and business development.

"The difference is that you'll be presented with stuff that is cleared in a way that respects copyright yet preserves that 'free' experience.

"You will not be asked to pay until you want to pull the trigger, so it's a pretty friendly place to explore and discover music."

EMI is understood to be getting a cut of Qtrax's ad revenues, and will get valuable consumer data.

No firm date has been set for the relaunch, but the service will enter a test schedule later this year.