Apple continues to experiment with DVD-length video downloads: it now offers a 21-video clip collection of Tori Amos as a complete digital set.

The 21 video clips are already available as a DVD release, called 'The Tori Amos Video Collection: Fade to Red'. Individual videos cost £1.89 or you can buy the whole collection for £14.99. The DVD's set retail price is £19.99.

Apple is also offering video compilation albums consisting of six or seven video clips from various artists, and also sells videos with their corresponding single. For example, the new Massive Attack 'Collected' album, released today, ships with video content.

Apple began selling its first full-length DVD in the US this month, a made-for-TV Disney movie called 'High School Musical'.

The company is widely expected to launch a full-length movie download service, perhaps as soon as April.

Last week, Universal Pictures confirmed a deal with the UK firm Lovefilm to sell movies online in Windows Media format. Users of this service can buy a version of the movie for download to their PC. They also receive a version of the movie for portable devices and are posted a full DVD of the movie.

Speaking to Reuters, Apple's head of iTunes Eddie Cue described video sales as a "natural fit" for iTunes users. "These are not replacements for people buying individual songs or albums. But they're great for well-established artists with a fan base behind them that wants more product (sic)."