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Major music publishers already locked in court with artificial intelligence firm Anthropic fired a second legal salvo Wednesday, filing a new lawsuit seeking more than $3 billion and accusing the company of sweeping, newly uncovered copyright violations involving sheet music and songbooks.

The case, filed in California federal court, deepens one of the most closely watched clashes between the music industry and generative AI developers, raising the stakes in what publishers describe as a fight to protect the backbone of the creative economy.

Publishers Say New Infringement Was Hidden

The plaintiffs — a roster that includes Universal Music Publishing Group and Concord Music Group Inc. — say the latest claims are “distinct and separate” from those raised in their earlier lawsuit against Anthropic. The new action centers on thousands of additional songs and, according to the publishers, could rank among the largest non-class action copyright cases ever brought in the United States.

In court papers, the publishers accuse Anthropic of continuing to use their copyrighted works without authorization while training and publicly releasing successive versions of its AI chatbot, Claude — even after the first amended complaint was filed.

They argue the company pressed forward despite publicly touting the adoption of so-called “guardrails” meant to prevent infringement.

From Hundreds of Songs to Tens of Thousands

The initial lawsuit, filed in October 2023, focused on just under 500 musical compositions that publishers said were improperly used to train Claude. The new Anthropic Music IP Suit dramatically expands that scope.

According to the complaint, publishers later learned that Anthropic had separately torrented millions of copyrighted books from pirate libraries, many of which allegedly contained sheet music and songbooks. They say this activity only came to light in July 2025, after U.S. District Judge William Alsup issued a ruling in a related case brought by book copyright owners against Anthropic.

That decision, publishers contend, publicly exposed Anthropic’s alleged torrenting practices for the first time.

Songbooks, Torrenting and Lost Revenue

The new lawsuit alleges Anthropic downloaded “countless pirated copies” of songbooks and sheet music through BitTorrent, naming well-known works such as Sweet Caroline, Bennie and the Jets, Eye of the Tiger, Have You Ever Seen the Rain, Bittersweet Symphony, She Will Be Loved, Viva La Vida, California Gurls and Radioactive.

When Anthropic used BitTorrent, the publishers say, it did not merely download the works — it also automatically uploaded unauthorized copies to other users, violating the publishers’ exclusive distribution rights and fueling further infringement.

Each pirated file may have been shared thousands or even tens of thousands of times, the complaint alleges, resulting in substantial lost revenue. The publishers also accuse Anthropic of helping sustain pirate libraries by participating in the very systems that enable widespread infringement.