Lawyers for Marvin Gaye’s heirs and recording artists Pharrell and Robin Thicke were singing past each other in court Friday.

Ninth Circuit Judge Milan Smith repeatedly complimented Quinn Emanuel Urquhart & Sullivan partner Kathleen Sullivan and Arnold & Porter Kaye Scholer partner Lisa Blatt on the forcefulness of their arguments in a copyright infringement case that has lit up the music industry.

But it wasn’t clear which side was making the most headway with the appellate court. All three judges put the lawyers on the spot over various aspects of the $5 million jury verdict arising from the song Blurred Lines.

Sullivan framed the verdict in Williams v. Gaye as conflating ordinary artistic inspiration with copyright infringement. Jurors should not have been instructed that Thicke and Pharrell Williams might have subconsciously infringed Gaye’s “Got to Give It Up”—especially not after hearing evidence that the two discussed the song before recording Blurred Lines, Sullivan argued. “This case was turned into what it shouldn’t have been—a case about inspiration,” Sullivan told the court.

Judge Jacqueline Ngyuen picked up that theme at one point, telling Blatt that “every single artistic creation is inspired by prior works.”

But Blatt—and the court—spent much more time debating a threshold issue: whether Kronstadt properly limited the basis for infringement to sheet music Gaye’s publishers deposited with the Copyright Office. Blatt argued that jurors should have been allowed to consider the actual recording of “Got to Give It Up.”

“The theme of this case is that both hands were tied behind the Marvin Gaye heirs’ backs, they were blindfolded and handcuffed, and still won the trial,” Blatt said.

Smith seemed to agree that Kronstadt’s reading of the 1909 Copyright Act would deprive numerous recording artists of copyright protection. “Elvis Presley couldn’t write his own music,” he said at one point.

Blurred Lines became an international sensation in 2013. Thicke, Williams and Clifford Harris are credited as co-authors. In an interview with GQ magazine, Thicke recalled telling Williams that “Got to Give It Up” was one of his favorite songs of all time, and that “we should make something like that, something with that groove.” The two started playing and “we literally wrote the song in about a half hour and recorded it.”

Gaye’s heirs sued for infringement a few months later. In his deposition Thicke said he had told lies in the GQ interview and others like it “to help sell records.”

The Los Angeles federal court jury awarded about $7.3 million, which Kronstadt reduced to just over $5 million, plus a 50 percent running royalty.

Sullivan argued Friday that the magazine articles never should have come into evidence. Blatt replied that they were admissible to prove willfulness and as impeachment evidence.

The Ninth Circuit judges seemed more dialed in on the exclusion of Gaye’s recording. Kronstadt ruled that recordings made prior to the 1976 Copyright Act are not admissible to prove substantial similarity. Instead, each side was allowed to present expert witnesses who interpreted the protected elements of the “lead sheet,” which is a written sketch of the song deposited with the Copyright Office.

Blatt called this “a made up notion” that would render every artist who wasn’t fluent in written music “second-class citizens.” Blatt’s co-counsel, Richard Busch of King & Ballow, said that in every music copyright case “since the beginning of time, the recorded composition has been the basis of the claim.”

Smith asked Busch to cite a few examples, but he could only come up with two. Judge Mary Murguia suggested that one of them, Three Boys Music v. Bolton, isn’t on point, while the other is from a different circuit.

Blatt argued that even under the “Kafka-esque” rules of the trial, her clients properly prevailed. “There’s 600 pages of transcript arguing about what was in the lead sheet, and the jury voted our way,” she said. “They just lost on this factual issue. It happens in trials.”

Sullivan, meanwhile, said that her opponents had “completely misrepresented” Three Boys and the law of sound recording. She argued that the Gaye heirs’ experts went beyond “interpreting” the lead sheet. “They embellished the lead sheet. They changed the lead sheet. They rewrote the lead sheet. They put thing in that weren’t in the lead sheet. And that’s what took this case off the rails,” she said.

As in the briefs, Sullivan invited the judges to listen to Blurred Lines and then what she called “the relevant comparison,” a recording of the protectable elements of the sheet music performed by her side’s expert witnesses. Blatt described it as a “lobotomized, emasculated” recording that bears little resemblance to the orginal song.

The court didn’t sound inclined to make its own assessment. “You’ve got three real experts here, right?” Smith said.

“Well, you have law clerks, you honor,” Sullivan replied, prompting laughter from Smith.