Grooveshark just can't seem to shake its copyright woes.

A group of songwriters and music publishers filed a lawsuit on July 15 in Tennessee against the digital-music service, claiming Grooveshark enables users to obtain music illegally and therefore is liable for copyright infringement, contributory infringement, and vicarious infringement.

Grooveshark, based in Gainesville, Fla., is a service that offers free music by enabling users to post their own tracks to the site and then share them with other users.

Grooveshark's "users and subscribers are actively infringing plaintiffs' copyrighted musical compositions," the plaintiffs said in their complaint, filed in U.S. District Court for the Middle District of Tennessee. "Defendant neither sought nor obtained a license, permission, or authorization from plaintiffs."

Among the plaintiffs are Mark Farner, who made a name for himself as the lead singer of Grand Funk Railroad, and Mark Weiss, the songwriter who penned the hit 1970s tune "Rhinestone Cowboy." A Grooveshark representative wasn't immediately available for comment, but the company has said in the past that it obeys the rules of the Digital Millennium Copyright Act and maintains that as a service provider, it is protected against any copyright violations committed by its users.

Grooveshark already is locked up in a legal battle with Universal Music Group, the largest of the four top record companies. Previously, EMI Music had filed suit against the company but that was settled. In April, Google responded to complaints from the Recording Industry Association of America by removing Grooveshark's app from the Android Market.

This isn't the kind of news that Grooveshark can use right now. All the momentum in the digital music sector seems to be with newcomer Spotify, the European service that has finally landed in the United States, and Turntable.fm. Spotify is fully licensed and Turntable seems to be headed that way. The company announced this week that it had struck agreements with two major music-rights groups.