Amazon has announced a deal with Sony BMG to offer DRM-free songs from Sony artists on Amazon's MP3 music download service.

The deal will make Amazon the only retailer to offer DRM-free MP3s from all four major music labels, as well as more than 33,000 independent labels.

"We are constantly exploring new ways of making our music available to consumers in the physical space, over the internet and through mobile phones," said Thomas Hesse, president of global digital business and US sales at Sony BMG.

"This initiative is the newest element of our ongoing campaign to bring our music to fans wherever they happen to be."

Amazon MP3 was launched in the US in September 2007 and boasts the world's biggest selection of DRM-free music downloads at over 3.1 million songs from more than 270,000 artists.

Tracks are available exclusively in the MP3 format without DRM software and are encoded at 256Kbps.

"We are excited to offer Amazon MP3 customers DRM-free MP3s from Sony BMG, which represents many of the most popular musicians from the past and present," said Bill Carr, vice president for digital music at Amazon.

Most songs are priced from 89 to 99 cents, and most albums are priced between $5.99 and $9.99.