The world's biggest record company, Universal Music, is suing two video-sharing websites in the US.
Mariah Carey is one of Universal's most successful artists
The firm, whose artists include U2 and Mariah Carey, accuses both Grouper and Bolt of allowing "mass infringement" of copyright by letting users swap videos.
It wants damages of up to $150,000 (£80,000) for each video distributed on the websites without permission.
Bolt's chief executive, Aaron Cohen, maintains his site removes copyrighted material as soon as it is notified.
"There's no question that people upload copyrighted content from time to time," he told Reuters news agency.
"Occasionally we receive official notices to remove content and we do."
Thousands of viewers
According to Universal's legal case, Grouper has become "prominent" and "valuable" through its "use and exploitation of copyrighted material".
The recording company cites a simple search of Grouper's website, which reveals a number of Mariah Carey videos available for download.
One clip, for her hit single Shake It Off, has been viewed more than 50,000 times.
"Grouper and Bolt cannot reasonably expect to build their business on the backs of our content without permission," said a Universal spokesman.
The firm said it retained the right to add Sony Pictures, which bought Grouper for $65m (£34m) in August, as a defendant at a later date.
Neither Grouper nor Sony was available for comment.
Video-sharing websites have been one of the year's biggest internet success stories, allowing people to swap home-made videos and amateur films online.
YouTube's founders sold their company to Google for $1.65bn
Last week, Google bought the most successful example - YouTube - for $1.65bn (£883m) in shares.
Launched in February 2005, YouTube has grown quickly into one of the most popular websites on the internet.
It attracts 72 million visitors a month, compared to 8.1 million for Bolt and just 1.8 million for Grouper.
However, it has managed to secure a deal with Universal Music which allows it to host music videos by the company's artists.
Universal says it also sought licensing deals with both Grouper and Bolt, but failed to reach an agreement with either party.