iTunes Plus is launching with EMI’s digital catalog of recording artists including Coldplay, The Rolling Stones, Norah Jones, John Coltrane and Pink Floyd.

"Our customers are very excited about the freedom and amazing sound quality of iTunes Plus," said Steve Jobs, Apple’s CEO. "We expect more than half of the songs on iTunes will be offered in iTunes Plus versions by the end of this year."

Users of iTunes Plus will be able to download songs from EMI artists without limitations on the type of music player or the number of computers that purchased tracks can be played on.

iTunes is also offering users a one-click option to upgrade previously purchased EMI content to the iTunes Plus versions. EMI music videos are available in iTunes Plus versions with no change in price.

"This is a tremendous milestone for digital music," said Eric Nicoli, CEO of EMI Group. "Consumers are going to love listening to higher quality iTunes Plus tracks from their favorite EMI artists with no usage restrictions."