Boring music, not file swapping alone, is causing falling sales of music CDs, according to research from NPD Group.

The analyst group warned record companies that unless they address this factor they will not reverse market decline.

The music industry has been waging a long-running series of legal battles against peer-to-peer sites, which it blames for the slump in music CD sales.

Last year, sales in the US fell by 13 per cent, and were down another nine per cent in the first quarter of 2003.

But the year-long study from NPD into the buying habits of internet users showed that, even though 60 per cent of music buyers had never downloaded free music, CD sales for this group had still declined by seven per cent.

NPD Group attributes more than half of the slump to free file-sharing activity on services like Kazaa and Morpheus, but it also said that a significant portion of the decline came from older music buyers.

This group, which is not generally associated with illegal file sharing or digital piracy of any kind, complained of a dearth of interesting new material.

"Our research shows that even if digital file sharing were to disappear tomorrow, the record labels and retailers would still need to overcome important underlying causes of recent market declines," said Russ Crupnick, NPD's vice president.