Apple is expected to refresh its iPod line today, and although the company has been characteristically silent on precise details of what will be announced at its annual September product launch, the big money is on a slimmer iPod nano and a cheaper iPod touch.

The event, which takes place at 1pm EDT, has been given the tag line 'Let's Rock' by Apple's PR machine, indicating that the announcement with centre on iTunes or the iPod range.

In an interview with Computerworld US, Technology Business Research analyst Ezra Gottheil seconded the music angle, but was more specific. "They'll probably bring down the price of the iPod touch to make it more appropriately priced in comparison with the iPhone," said Gottheil.

Gottheil also predicted Apple may finally launch a subscription service for the iPod, while talk of a flat-fee iTunes Unlimited has been ongoing for several weeks. These moves were originally predicted in March, when the Financial Times reported Apple to be in the negotiation with music labels in order to offer iTunes users full access to music at a flat rate.

Meanwhile, Digg founder Kevin Rose said last month that the company would release a new, slimmer version of the iPod nano.

An outside bet would be new models or tweaked specifications for Apple's MacBook and MacBook Pro product lines. "They could announce something in the notebook field," said Gottheil, "though they have their back-to-school promotion running through next week".

In Apple's last three September launch events, the company introduced the iPod nano in 2005; overhauled the shuffle, nano, and video-capable iPods in 2006, and rolled out the third-generation iPod nano in 2007. Other September surprises in recent years have included partnerships with Motorola, car makers, the NFL, and Starbucks.

See also:

iPod nano review

iPhone 3G review

iPod touch review