Apple has introduced its fourth generation iPod, with a new interface similar to that found on the iPod mini and a new feature called Shuffle Songs. The new iPod also sports a battery that's good for up to 12 hours of use at a time, according to Apple.

The iPod's new Shuffle Songs feature is a new command that appears in the main menu. Activating Shuffle Songs causes the iPod to shuffle the songs in your active playlist (or all songs on the iPod).

The iPod's new Click Wheel is similar to the interface found on iPod Minis: It's a continuous-scrolling surface that features five push buttons: a centre button, a menu button positioned at 12 o'clock, fast forward and rewind buttons positioned at 3 and 9 o'clock, and a play/pause button positioned at 6 o'clock. Apple said the Click Wheel offers users better one-handed navigation. The iPod is available in 20GB and 40GB capacities for US$299 and $399 respectively.

The iPod is available in 20GB and 40GB capacities for $299 and $399 (around £165 and £220) respectively. The new battery on the iPod is good for up to 12 hours of juice at a time. The iPod previously sported a battery good for about an 8 hour charge, under optimal conditions.

Apple previously made available three models of iPods: 15GB, 20GB and 40GB systems, with prices at $299, $399 and $499 (£165, £220 and £275). The 15GB model has been dropped all together. A new high-capacity iPod is notably absent from Apple's line-up with this release.

Toshiba announced in June a new 1.8-inch 60GB hard disk drive that it said had already been ordered by Apple. That new drive was expected to be available to manufacturers in July or August at the time of its unveiling.

HP iPod coming in September

In January Apple and HP announced a partnership that would allow HP to sell its own branded iPods, manufactured by Apple. Although HP-branded iPods still aren't shipping, HP CEO Carly Fiorina noted on Monday that her company would begin shipping its own version of the iPod in September. "We decided to wait for this amazing new fourth generation iPod, as it will offer our customers an even better experience," said Fiorina.

Apple and HP's partnership has already yielded a positive benefit for Apple: Its iTunes software is already shipping pre-installed on a large quantity of Windows-based PCs sold by HP.