Just a couple of months after it announced a key deal with Warner Music Group, the free, ad-supported P2P music service Qtrax has officially relaunched in the United States.

"Over 95% of all digital music consumption may be illegal," says Allan Klepfisz, Qtrax's president and CEO. "And the legal sites only offer free streaming. Qtrax offers free high quality downloads. Qtrax will monetize all digital plays by sharing advertising revenue and offers a content rich environment that delivers a clearly superior consumer experience to any of the popular pirate sites."

"Qtrax, which is in part targeted at consumers currently using illegal peer-to-peer 'torrent' sites, will launch into an increasingly crowded and fast-changing competitive landscape," warns the Financial Times' Andrew Edgecliffe-Johnson. "Apple's iTunes, the dominant digital music store, this week shed its one-time adherence to 99 cent pricing for all tracks to introduce variable pricing, while streaming services such as Pandora and Spotify have challenged the iTunes download model."

"The Qtrax relaunch comes just weeks after another ad-supported music download service — SpiralFrog — closed down after it could not meet its debt obligations," notes Billboard's Antony Bruno. "The SpiralFrog situation has cast a shadow of doubt on the viability of ad-supported music download services at a time when ad-supported streaming services like imeem and Spotify are taking center stage."

More here from the WSJ ... and the press release is here.