Universal Music Group, a division of Vivendi SA (LSE: VIV), announced plans yesterday to test the sale of tracks without Digital Rights Management technology with vendors Amazon (NASDAQ: AMZN), Google (NASDAQ: GOOG), and Wal-Mart (NYSE: WMT), according to Reuters. Notably absent from the trial is Apple Inc. (NASDAQ: AAPL)'s iTunes Store, but DRM-free MP3 tracks will still be playable on the iPod, in addition to various other players.

Universal's trial run is set to last through January, allowing the largest of the four major music companies to "analyze such factors as consumer demand, price sensitivity and piracy in regards to the availability of open MP3s."

With the test run, Universal joins EMI Group PLC (LSE: EMI) as the only two of the four major music labels to offer DRM-free tracks for sale. Warner Music Group (NYSE: WMG) has remained staunchly in favor of the technology, while Sony (NYSE: SNE)'s BMG Music Entertainment has made hints that it may too explore DRM-free tracks, but remains with the protective technology.

Apple's absence from the trial could hint at record labels' displeasure with the company, or perhaps it's simply a method to ascertain a test run away from the third-largest music retailer. iTunes has offered EMI's DRM-free tracks as part of a new "iTunes Plus" service since late May. Those tracks run 30 cents higher than DRM-encoded tracks, but it is not known whether Universal will adopt a similar price scale during its trial.