A new music download service is promising free legal tracks to users who agree to watch adverts.

SpiralFrog has teamed up with Universal Music Group, which publishes artists such as Elton John and Eminem, to offer ad-supported music to surfers in the US and Canada. 

Under the agreement, SpiralFrog will have access to Universal's back catalogue. In exchange for viewing adverts, customers will be permitted to download tracks free of charge.

Downloaded tracks will still be protected by digital rights management technology, however, to prevent unauthorised copying.

Robin Kent, chief executive at SpiralFrog, claimed that the service will offer consumers a better experience than that of pirate music sites, with no risk of viruses or spyware.

"Piracy continues to be one of the biggest issues facing the music industry where illegal file sharing and unauthorised CD burning are the prime means of music piracy," he said.

Ovum analyst Michele Mackenzie added: "There are already hundreds of music service providers in the European market, most of which are struggling to compete with Apple's dominant iTunes/iPod ecosystem.

"We expect more providers to explore this avenue as a larger share of advertising revenue shifts from traditional to online media." 

However, Mackenzie warned that the advertising pot is not bottomless. "Those that succeed in attracting advertising revenue will be those that can guarantee advertisers the right audience," she said.

"Few service providers are currently in a position to provide the large audiences that advertisers require, and few pure music providers have the heritage of building a business funded by advertising.

"SpiralFrog [also] does not appear to have a portable or mobile component, which again would be a faux pas in an age when users want to be able to port their music to other devices and take it with them."

The service, aimed at 13 to 34 year-olds, will launch later this year.