• by Wendy Davis , Staff Writer @wendyndavis, April 15, 2008

Amazon has been growing its digital download sales without cutting into Apple's bottom line, according to new research from NPD Group.

Around 90% of the people who purchase MP3s from Amazon have never used iTunes, according to the report, as per Ars Technica. Additionally, the stores are attracting different customers, with men accounting for 64% of Amazon buyers, but just 44% of iTunes buyers.

The report is taken as a sign that digital music stores have plenty of room to grow -- which is good news not only for iTunes and other established sellers, but also for new entrants like MySpace, which is gearing up to launch its own DRM-free digital music store.

At the same time, Apple eventually will have to arrange to sell DRM-free tracks if it hopes to remain competitive. For now, Apple still sells far more music downloads than rivals, including Amazon.com. But Amazon has a significant advantage in that it can offer DRM-free tracks from all of the major labels. Only one label, EMI, allows Apple to sell music free of the digital rights management software that makes it difficult to copy or play on devices other than iPods.