Amazon's offering is about one-third of Apple's catalog, which has more than
6 million songs. ITunes was the largest online music store in 2006, with 70% of the market, according to research firm NPD Group. Amazon's music download service, called Amazon MP3, includes more
than 180,000 artists from 20,000-plus labels, and the music is being sold without digital rights management, or DRM, software. That allows consumers to listen to downloads on any device they choose.
Music is downloaded through Amazon MP3 software, which then transfers the music to a buyer's iTunes or Windows Media Player library. Songs also can be burned to compact discs.
Major music labels Universal Music Group and EMI Music have signed on to sell their tracks on Amazon, as have thousands of independent labels. But Warner Music Group Corp. and Sony BMG Music Entertainment have not agreed to sell music on Amazon MP3.