DRM-free music sells at a much higher rate online than protected music, according to UK-based digital music store 7 Digital. In fact, customers buy it four times as often as they do DRMed music. As a result, almost 80 percent of the store's sales are of DRM-free content. 7 Digital may not sound familiar to some, but it carries over 3 million songs and has many selections from major artists in addition to independent labels.

"MP3 is the only truly interoperable format that works with the iPod, most mobile phones (including the iPhone) and all MP3 players," said 7 Digital's Ben Drury in a statement. "Consumers are a lot savvier than some people think."

The availability of DRM-free music is not only good for track sales, it's doing favors for full album sales too. 7 Digital said that customers buying unprotected music are more likely to buy albums than those buying music with DRM, with some 70 percent of MP3 sales being part of full album downloads.

This should come as good news to the music industry, which has long seen album sales suffer since the proliferation of music stores that allow customers to cherry-pick tracks (which includes pretty much every music store these days). Music labels have been trying to come up with incentives to entice customers to buy more at a time, such as offering exclusive content that only comes with an album purchase. Some artists still stand by the album format, too, at the risk of selling fewer tracks overall. Hip hop artist Jay-Z recently made a decision to withhold his most recent album, American Gangster, from the iTunes Store because he didn't want the tracks to be sold individually.

So far, EMI is the only major music label to fully embrace DRM-free music sales. EMI now sells its music without copy protection on any music store that wants to participate, which includes the iTunes Store and Amazon's music store. Universal is still experimenting with DRM-free downloads on select music stores, but otherwise Sony BMG and Warner are still slow to catch up. With news like this, though, they might be more likely to give DRM-free music a try.