Digital rights management (DRM) music restrictions are finally on their way out. Apple, which accounts for the majority of all U.S. music sales, has released its 10-million-track catalog from those constraints. DRM restrictions imposed by Apple and its competitors have limited both the number of PCs that can play songs and the kinds of devices that can read the files (you couldn't play a typical iTunes purchase on a Zune, for example). With the restrictions lifted, you'll be able to buy music from iTunes--or another store--for use however you want.

Competition is now wide open for these interoperable music files. Besides iTunes, millions of DRM-free files are available from Amazon, Rhapsody, Napster, Zune, eMusic, and others. But each store has its own benefits and limitations: price, file quality, selection, and other quirks. Here's how they all stack up in the DRM-free download world.

iTunes

Apple's lock on the MP3 player market vaulted its iTunes music store ahead of others. The store requires you to shop through iTunes software and is designed to work with iPods, but you can move purchased songs into Windows Media Player, with a caveat: iTunes doesn't actually sell MP3s.

Its "iTunes Plus" tracks--the DRM-free ones--are AAC (advanced audio codec) files. This format isn't proprietary to Apple, though the company is one of its most visible supporters. So in addition to iPods, DRM-free AAC tracks work on nearly all music players, including the Zune and even many mobile phones. Just be sure to buy the "iTunes Plus" songs and not the Apple-only DRM tracks until the transition is finalized.

If you previously bought those restricted songs, you can upgrade them to open files at a cost of 30 cents per track or $3 per album. Apple says that all of its DRM-free AAC tracks are encoded at 256 kbps at a variable bit rate. Bit-for-bit, I tend to prefer the quality of AAC over MP3, but preferences vary. And while AAC is fairly universal, MP3 is still more-commonly supported.

The strong iTunes store interface is an easy pick if you use Apple's iPod or iPhone. Tracks have cost 99 cents until now, but the DRM-free change is adding 69-cent and US$1.29 price points. Album pricing will also vary more; $9.99 will remain typical, however.

Rhapsody

Rhapsody uses a Web-only interface to browse its stock of 7 million songs. The service is still split between subscription and DRM-free MP3s, so surf the MP3 section for the DRM-free songs.