Amazon signs Sony download deal

The deal means Amazon is now the only company offering tracks from all four big music companies free of DRM.

This makes the Amazon store a more significant rival for Apple iTunes which has long had a commanding lead over rivals in the downloadable music market.

All the 3.1 million tracks in the Amazon store are free of DRM software. In contrast, only songs from EMI and some independent labels are available via Apple's iTunes without copy controls.

In February 2007, Apple boss Steve Jobs called on record labels to stop using DRM in a bid to boost the popularity of downloadable music.

The Amazon MP3 store, which launched in September 2007, is only available in the US. There have been no announcements about when or whether the service will be expanded overseas.

Songs prepared in the MP3 format can be played on any portable music player.