Ten record companies have joined forces to sue music website MP3.com for alleged copyright infringement, seeking damages that could run into billions of dollars.

EMI, Warner, Bertelsmann and Sony are all involved in the suit, which was filed in New York by the Recording Industry Association of America.

They allege that their copyrights are being violated by two services introduced by San Diego company MP3.com less than two weeks ago.

'Cartel'

These allow consumers to access music from CDs they already own from MP3.com's site via a PC or portable player, or listen instantly online to copies bought from the company's partners.

Michael Robertson, founder and chief executive of MP3.com, said the lawsuit was an attempt at intimidation by a "cartel" of major record companies.

He said he would fight it "to the court of last resort if necessary".

Mr Robertson believes that the services will stimulate CD sales and be "a financial boon for the music industry overall".

Surfers' delight

MP3 - the digital format that allows music to be stored, swapped and downloaded straight from the internet - is said to have overtaken "sex" as the most frequently searched term on the web.

Surfers are looking for sites offering music they can download to their PC - immediate music, often available free.

MP3 is upsetting the commercial music industry because it threatens to overturn the established methods of signing up performers and controlling revenues from selling their wares.

Big business

Walkman-style MP3 players are widely available for around �100 and demand for music in MP3 format is booming.

Almost 70% of surfing music-lovers in the UK have already used the format, and analysts are predicting it will more than double the value of the music industry from �25bn to �62bn.

Michael Robertson says: "Artists and labels can employ MP3 technology in the best way to suit their individual needs.

"Give away one song to sell a CD, distribute low-quality versions of songs, sell individual songs for digital delivery, add an audio commercial to songs - there are limitless possibilities for artists to explore."

He says he plans eventually to charge users for his service, using funds to pay royalties.

What is MP3 again?

It is a freely available technology for compressing sound - music or speech - into a small file about one-twelfth the size of the original.

The key thing about it is that it comes close to the sound quality of the original.

Any file compressed in this way is easily identified by the filename suffix .mp3.

What every MP3 user should watch out for, however, is the risk that they could be listening to music in breach of copyright.

As it is so easy to create MP3 files from CD selections and make them available on websites for downloading, promoters of the MP3 format have often been accused of encouraging copyright violations.

Agreeing a standard

MP3 enthusiasts claim that what publishers are afraid of is any method of distribution other than on CD. They say that if CD sales are lost to piracy, many are sure to be generated by exposing people to more music, who then buy CDs by bands they would not otherwise have ever heard.

What has been hampering the spread of MP3 technology is the inability, so far, of the music industry to agree a secure distribution and copyright management standard.

Several websites are promoting MP3 as both a high-quality audio format and as a way for self-publishers to gain ready access to an audience.

Some music publishers are also providing sample cuts in MP3 format as a way to entice users to buy a CD. But not much mainstream copyrighted material is available yet, except as illegal downloads.