Apple's iTunes service this morning added an extensive catalogue of music from another Beatle, the late George Harrison.

The front page of the iTunes UK site now carries a pane advertising the addition of the artist's catalogue: "George Harrison, catalogue and exclusives, just added," the pane declares. Nine albums have been made available initially, with the rest of his catalogue set to be made available later this year.

Cicking on the link leads fans to a page offering just one single track, but Apple sources this morning told Macworld UK that access to further material by the artist "has just been switched on". This means access to the music is likely to unfold during the day, as the system propagates itself.

The move to make George Harrison's music available through iTunes means Apple's service now offers music from all four Beatles: Paul McCartney, Ringo Starr, John Lennon and Harrison. The move also makes it far more likely that music from The Beatles will soon be made available through iTunes.

Speaking earlier this year, the widow of George Harrison, Olivia Harrison, explained that agreements to make music from The Beatles available through online music services were being made, but warned that fans of the Liverpool band may have to wait until next year until the process is put into effect.

On the release of the artist's work through iTunes, Olivia Harrison said: Olivia Harrison said: "It is exciting that George's catalogue is finally available for downloading. He had begun the digital remastering of his albums but had no idea how the digital world would change the way we access and listen to music."

In related news, iTunes is also making an album featuring the music of John Lennon available. The album, Instant Karma: The Amnesty International Campaign to Save Darfur, features cover versions of tracks taken from Lennon's seminal Instant Karma album and is a fundraising venture on behalf of Amnesty International's campaign to promote international action to protect the afflicted population of Darfur.

Music from Lennon's album is performed by a range of artists, including Aerosmith, Ben Harper, Green Day and many more (66 performances in total).

The move to make Harrison's music available legally online for the first time comes just one week after Radiohead's high-profile move to make its new album available to fans online on a "pay what you like" basis. It also follows The Charlatan's recent decision to make the new album available for free download through the XFM website.

The battle for digital may have reached a critical point, but industry logjams remain, as shown by the $222,000 fine imposed against a file-sharer last week for the illegal sharing of 24 music tracks.