By Ian Youngs BBC News entertainment reporter

Unauthorised guitar tabs and other musical scores are widely available

The US Music Publishers' Association (MPA), which represents sheet music companies, will launch its first campaign against such sites in 2006.

MPA president Lauren Keiser said he wanted site owners to be jailed.

He said unlicensed guitar tabs and song scores were widely available on the internet but were "completely illegal".

Mr Keiser said he did not just want to shut websites and impose fines, saying if authorities can "throw in some jail time I think we'll be a little more effective".

Bitter battles

The move comes after several years of bitter legal battles against unauthorised services allowing users to download recordings for free.

Publishing companies have taken action against websites in the past, but this will be the first co-ordinated legal campaign by the MPA.

The MPA would target "very big sites that people would think are legitimate and very, very popular", Mr Keiser said.

"The Xerox machine was the big usurper of our potential income," he said. "But now the internet is taking more of a bite out of sheet music and printed music sales so we're taking a more proactive stance."

Music publishers and songwriters will consider all tools under the law to stop this illegal behaviour David Israelite National Music Publishers' Association

David Israelite, president of the National Music Publishers' Association, added his concerns.

"Unauthorised use of lyrics and tablature deprives the songwriter of the ability to make a living, and is no different than stealing," he said.

"Music publishers and songwriters will consider all tools under the law to stop this illegal behaviour."

Sandro del Greco, who runs Tabhall.co.uk, said the issue was not serious enough to warrant jail time and sites like his were not necessarily depriving publishers of income.

Learn

"I play the drums mainly but I play the guitar as well. I run the website and I still buy the [tab] books," he said.

"The tabs online aren't deadly accurate so if someone really wants to know it they'll buy the book.

"But most of the bands I listen to don't have tab books to buy so if you get them online, that's the only way you can really learn it unless you work it out yourself."

The campaign comes after lyric-finding software PearLyrics was forced off the internet by a leading music publishing company, Warner Chappell.

'No alternative'

PearLyrics worked with Apple's iTunes, searching the internet to find lyrics for songs in a user's collection.

"I just don't see why PearLyrics should infringe the copyright of Warner Chappell because all I'm doing is searching publicly-available websites," PearLyrics developer Walter Ritter said.

"It would be different if they had an alternative service that also provided lyrics online and also integrated [with iTunes] like PearLyrics did. But they don't offer anything like that at all."

A Warner Chappell statement said the company wanted to ensure songwriters were "fairly compensated for their works and that legitimate sites with accurate lyrics are not undermined by unlicensed sites".