The format war among music download stores has become a battle of acronyms, with some companies basing their marketing campaigns on the efficiency of their proprietary technology, but experts believe this could be a mistake.

Professor of Legal Informatics at the School of Law of the University of Milan Giovanni Ziccardi said: "The diffusion of different compression and anti-piracy systems will hardly be understood by consumers."

What consumers will understand, notes Reuters: is that "the music they bought on the Internet is shackled and bound compared with free-roam compact discs."

Sony European manager for network applications and content services Robert Ashcroft told "ATRAC is certainly part of our marketing message. When you have the better technology, you want to shout it from the rooftops."

ATRAC is Sony's proprietary technology that it claims allows consumers to "store more songs on a personal computer or digital music player while retaining the best sound quality, and more hours playing time on a single charge than rivals' technology".

Apple makes similar claims about the AAC format and its FairPlay software.