Apple has started shipping music tracks without digital rights management (DRM) technology. 

The songs can be found in the new iTunes Plus store and are limited to the EMI record label.

Apple chief executive Steve Jobs predicted that more labels would follow. " We expect more than half of the songs on iTunes will be offered in iTunes Plus versions by the end of this year," he said in a statement.

With the launch of iTunes Plus, Apple is making good on its promise in April to start offering DRM-free tracks by May.  

The music is 25 to 30 per cent more expensive than songs with DRM, at $1.29 in the US and 99p in the UK. Users can upgrade previous iTunes purchases for 30c or 20p per song.

Music in the iTunes Plus store is encoded at the higher 256Kbps AAC quality compared to the 128Kbps of regular content.

AAC encoded files can be played on iPods as well as computers running the iTunes media player. But the lack of DRM will allow consumers to convert the file to different formats such as the universally supported MP3.

Apple's iTunes is the first major online music store to ship music without digital protection. Amazon has publicly stated that it plans to sell unprotected MP3s.