And indeed, several online music stores that have the makings of a site as useful as Amazon's have had trouble getting record companies' permission to offer album samples, and their prices are typically little lower than those of physical music stores.

ECONOMIST: Electronic commerce

Mash-up artist Girl Talk may have more than 300 samples on his new album, Feed the Animals, but creator Greg Gillis says that he has only 100 MP3s on his laptop.

NPR: Girl Talk Chops Pop Music To Pieces

This new agenda is best articulated in the soulful "Circulate, " in which Jeezy laments rising gas prices and unemployment rates alongside vocal samples of Billy Paul's prescient 1975 album cut "Let the Dollar Circulate".

NPR: Young Jeezy's 'Recession' Pushes Hope

The song, which was unofficially released as a free download single over the Christmas period, heavily samples Planet Telex, the opening track on Radiohead's second album The Bends.

BBC: Last Updated: Friday, 1 February 2008, 11:04 GMT