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.

Why a Second Lawsuit

The publishers say they attempted to amend their original complaint to include the newly discovered torrenting claims, but the court declined to allow it. Anthropic, they note, did not deny the torrenting allegations at that stage, instead arguing they were unrelated to the initial lawsuit.

As a result, the publishers said, a second lawsuit was unavoidable.

“Publishers therefore bring this separate action to address defendants’ egregious and willful infringement,” the complaint states, citing both the downloading and uploading of unauthorized copies through illegal websites.

A spokesperson for the publishers said Wednesday that the new filing reflects Anthropic’s “persistent and brazen infringement” of songwriters’ rights, including the continued use of lyrics in training new AI models and in the outputs those models generate.

The publishers say the case involves more than 20,000 songs and carries potential statutory damages exceeding $3 billion.

Anthropic did not immediately respond to a request for comment late Wednesday.

Judges, Guardrails and Ongoing Litigation

In the earlier case, U.S. District Judge Eumi K. Lee ruled last October that amended claims against Anthropic were sufficient to support allegations of contributory and vicarious infringement. She rejected the company’s argument that the publishers failed to show Anthropic knew — or was willfully blind to — how users might infringe copyrights using Claude.

Last month, Anthropic sought a court order compelling publishers to turn over the prompts and outputs used by investigators to test whether Claude reproduced song lyrics. The publishers criticized the request as overly broad and a renewed attempt to pierce work-product protections.

Parallel Fights in the AI Copyright Wars

The music case unfolds alongside other high-profile legal battles facing Anthropic. In a separate lawsuit brought by bestselling authors accusing the company of using their works to train AI systems, Anthropic agreed to pay $1.5 billion to resolve the claims.

The music publishers argue that, rather than changing course, Anthropic has intensified its conduct since the first lawsuit was filed — scraping data online, copying physical books and exploiting datasets that allegedly contain unauthorized copies of copyrighted music.

They contend Anthropic trains its models to memorize works, leading to outputs that replicate copyrighted material in multiple ways. Beyond that, they say, the AI generates vast quantities of new, AI-written lyrics derived from copyrighted songs, competing directly with legitimate works and harming songwriters.

A Call for Ethical AI

Publishers acknowledge the promise of artificial intelligence and say they have already begun exploring licensing deals that would permit authorized uses of musical compositions. But they stress that innovation must be built on respect for creators’ rights.

AI, they argue, should amplify human creativity — not erode it.

The publishers are represented by attorneys from Oppenheim & Zebrak LLP, Cowan Liebowitz & Latman PC, and Coblentz Patch Duffy & Bass LLP. Counsel for Anthropic in the new case was not immediately identified, though the company is represented by WilmerHale lawyers in the original lawsuit.