Amazon.com today launched an early version of its much-anticipated digital music download store, which is set to rival to Apple’s dominant iTunes Store. The service, dubbed Amazon MP3, includes a selection of over 2 million DRM-free songs from two of the four major record companies – EMI and Universal – plus thousands of independents.

Songs are encoded at 256 Kbps and priced between 89 cents and 99 cents, with more than 1 million songs priced at 89 cents, while most albums are priced from $5.99 to $9.99. Moreover, the digital rights management-free service means customers can use just about every portable music player – including iPods – and every desktop music application to play their songs, or burn them to CDs.

As expected, the actual song purchasing process is pretty painless and can be done using Amazon 1-Click. In addition, Amazon suggests users to install the Amazon MP3 Downloader, which will automatically add music downloads to iTunes or Windows Media Player and is apparently required for full album purchases.

All in all, Amazon MP3 seems to have one-upped iTunes Store in at least two areas: Bit rate and pricing. It will be interesting to see whether this is enough for the online retailer to challenge iTunes’ dominance.