The largest music download sites are taking the fight to Apple iTunes with a new secret weapon to stop the iPod music service - literally - in its tracks.

The Entertainment Retailers Association (ERA) has designed a new logo that emphasises the fact that MP3 files can be played on any digital player. Apple's iTunes-friendly AAC format plays only on the iPod and iPhone. Apple players also play other digital music formats, such as MP3.

The BBC reports that the UK trade body behind the initiative claims it will help consumers identify legal sites. (Are they implying that Apple's iTunes music store is somehow illegal, or that pirate and criminal P2P trading sites never share MP3s?)

HMV, Woolworths, 7digital, Digitalstores, Tescodigital, Tunetribe, and have all signed up to the scheme - as has the British record industry's trade association, the BPI.

ERA has lobbied record companies for months to adopt the MP3 standard, arguing that proprietory digital rights management (DRM) systems such as AAC have been a brake on legal download sales.

"The beauty of an MP3 file is that once you have bought it, you don't need to be a computer genius or a lawyer to make it work and you are not locked in to a relationship with a single retailer or hardware manufacturer," said 7digital's Ben Drury.

BPI chief executive Geoff Taylor said: "This logo will not only help give consumers confidence that the music files they are buying will play on a wide range of devices, but will also help them know that they are legal and that artists are getting paid."

The only trouble is that the logo is dull, colourless and generally a bit crap.

MP3 logo

(Not that Apple's rather dated iTunes logo is much better, with its 1990s CD and chunky emerald green musical note...)

Apple iTunes logo

And as Apple's iPod and iPhone are also MP3 compatible, I can't quite see the point. The iTunes Music Store doesn't sell MP3 files, but iTunes is MP3 compatible. Everything is MP3 compatible, that's the beauty of the standard.