Suno has asked a federal court to block Universal Music Group and Sony Music Entertainment from adding more than 61,000 sound recordings to their copyright infringement lawsuit against the AI music company.
In an opposition brief filed on Thursday (June 4), which you can read here, Suno argued that the labels “unduly delayed” in moving to expand the case, and that granting their request would deny the company a timely ruling on whether training its AI model on copyrighted music is fair use.
The filing was entered in the US District Court for the District of Massachusetts, where the case has been pending for nearly two years.
UMG and Sony asked the court on May 21 to add 61,026 recordings to the suit, after using audio-fingerprinting service Audible Magic to identify their recordings within Suno’s training data.
The original complaint, filed in June 2024, asserted 560 works.
Suno said the labels’ move followed the “standard playbook” of large rightsholders.
“This is a too-familiar page from the standard playbook of aggregate music rightsholders: file an action asserting ‘representative’ works, let the litigation proceed through discovery for years, then attempt to expand the list of works exponentially at the close of fact discovery,” Suno‘s lawyers wrote.
“This is a too-familiar page from the standard playbook of aggregate music rightsholders: file an action asserting ‘representative’ works, let the litigation proceed through discovery for years, then attempt to expand the list of works exponentially at the close of fact discovery.”
Suno’s opposition brief
The company said adding tens of thousands of works would require new discovery and delay a ruling on its fair use defense, pointing to two decisions in which courts found that training a generative AI model is a transformative use: Bartz v. Anthropic and Kadrey v. Meta Platforms.
“After two years of extensive fact discovery, Suno is entitled to a timely consideration of its fair use defense,” the filing stated.
“To the extent Plaintiffs believe they have additional infringement claims to assert based on other works, the proper course is to file a separate action, not undertake a wholesale rewriting of this one.”
In their motion, UMG and Sony rejected that reasoning as “meritless,” saying “the cause of any delay was Suno‘s ongoing refusal to provide Plaintiffs with the data in its possession.”
The dispute over the additional works is one of two fronts on which Suno and the labels are now fighting.
In a separate filing on Friday (June 5), which you can read here, UMG and Sony urged the court to reject Suno‘s bid to keep secret the total number of audio files it used to train its model.
Suno has argued that disclosing the figure would cause it “competitive harm”.
The labels countered that Suno had already conceded the scale of its copying.
In its answer to the complaint, Suno admitted that building its service “required showing the program tens of millions of instances of different kinds of recordings,” and that those recordings “presumably included recordings whose rights are owned by the Plaintiffs.”
“Having publicly acknowledged copying of that magnitude, Suno cannot credibly claim that disclosing a slightly more precise count of the audio files that its AI model trained on would reveal anything competitively sensitive.”
UMG and Sony Music
“Having publicly acknowledged copying of that magnitude, Suno cannot credibly claim that disclosing a slightly more precise count of the audio files that its AI model trained on would reveal anything competitively sensitive,” the labels wrote.
They said there was “no cognizable reason to shield from public view how many sound recordings – including Plaintiffs‘ recordings – Suno copied to build its service.”
The suit was filed in 2024 by the RIAA on behalf of all three major music companies, with Judge F. Dennis Saylor IV presiding.
Warner Music Group exited the case after settling with Suno in November 2025 and entering into a licensing partnership, leaving UMG and Sony as the remaining plaintiffs.
The latest filings landed days after Suno raised over $400 million in a funding round that valued the company at $5.4 billion.
Fact discovery in the Suno case is scheduled to close on June 26, though the parties have discussed extending the deadline into August.
Suno‘s rival Udio is facing a similar attempt to expand the recordings at issue in a separate case.
Udio, known legally as Uncharted Labs and sued by the same labels in June 2024, is fighting a copyright case against Sony Music Entertainment in the US District Court for the Southern District of New York.
On June 3, Judge Alvin K. Hellerstein vacated an order that had kept parts of the case under seal.
“My Order granting Defendants’ motion to seal … is hereby vacated,” Hellerstein wrote, adding that the parties “may brief that motion to seal … in the ordinary course.”
The sealed material relates to Sony‘s proposed second amended complaint, filed on May 22, in which the label alleges that Udio “copied and ingested” 30,442 of its recordings into the company’s AI models.
Sony says it identified those works after gaining access to Udio‘s training data, and is the only major-label plaintiff left in the case after UMG and Warner settled with Udio in late 2025.
Document production in the Udio case is also scheduled to close on June 26.Music Business Worldwide
