Apple has been forced to make changes to its legal music download service after users figured out how to swap songs without paying.

Details of how to tweak the iTunes service so that other users could share and record peoples? playlists without paying were published online.,P. Apple released an update to the software that many users fear will stop legitimate uses of the 'Rendezvous' sharing facility. The original intention was that people on a local network, such as one connecting two or more PCs in the same household, could listen to each others' paid-for downloads.

"Rendevous music sharing has been used by some in ways that have surprised and disappointed us," said Apple in a statement.

"Some people are taking advantage of it to stream music over the Internet to people they do not even know."

The iTunes upgrade is not obligatory and many users have said on internet newsgroups that they will refuse to download the new software.

The service is not yet available to UK consumers because of legal problems over copyright issues.