Amazon.com today said it is now selling unprotected music from Sony BMG, making the online retailer the first store to offer DRM-free songs from all four major music labels in MP3 format, according to a report from Reuters. Apple's iTunes Store announced the availability of iTunes Plus in early April, with unprotected MP3 music files from EMI's catalog at a slightly higher price.

Plummeting CD sales have driven the big labels to rethink their strategy of selling music to customers, and recent studies showed heightened interest in unprotected MP3 tracks amongst music lovers.

Sony BMG earlier this week became the last of the four major music labels to offer digital songs without copy protection in an attempt to accommodate listeners who are fed up with DRM-protected tracks that won't play on certain players or are limited to specific devices or software.