A subsidiary of Brilliant Technologies, Qtrax launched April 9 delivering free music from all four major labels as well as several indie imprints.

The service’s mode of operation is quite simple: Download and install the Qtrax Mozilla-enhanced music player and search and download music. Along with tunes, the player also serves up advertisements from Qtrax ad partners.

All songs on Qtrax are protected by DRM technology and are currently compatible with most Windows-based MP3 players, with the service promising iPod playability in the near future. Right now, Qtrax is only licensed to deliver free music in the United States, though the service will expand to “select territories” in the coming months.

Qtrax describes itself as the first “free and legal peer-to-peer music service,” and that it strips out the possible nasties that might come attached to P2P downloads such as spyware, adware and mayhem-creating malware. Although the DRM wrapping prevents users from trading Qtrax tracks on open P2P networks, it does enable sharing through the Qtrax system.

If this sounds familiar, you may be thinking of free music site SpiralFrog which closed in March after accumulating millions in debt. However SpiralFrog never completed deals with all four majors, thus leaving it with a limited music inventory.

On the other hand, Qtrax searches current P2P networks, allowing users to download from those nets only if Qtrax is licensed to distribute that music.

“Over 95 percent of all digital music consumption may be illegal. And the legal sites only offer free streaming,” said Allan Klepfisz, Qtrax president and CEO. “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.”

Click here for Qtrax.

Click here for the Qtrax press release.