In truth, the lawyers representing the two musicians knew exactly who Mr. Busch was. In the small world of high-powered entertainment lawyers, Mr. Busch, 49, has carved out a niche as a crusading outsider, winning cases that have had wide-ranging repercussions for the music industry. Among them are Bridgeport Music v. Dimension Films, which established that even the tiniest sample — a piece of one song used in another — needs legal permission, and F.B.T. Productions v. Aftermath Records, which led to a wave of litigation over how royalties are paid in digital music.

Compared with the polished style of many of the Hollywood litigators he has faced in court, Mr. Busch is a bit rough around the edges. One of his former clients, Joel Martin of F.B.T. Productions, a company connected to Eminem, proudly calls Mr. Busch “a street fighter.” He is known for extensive preparation and an aggressive style in depositions. At the “Blurred Lines” trial, he spoke so intensely that his voice cracked and the judge, John A. Kronstadt, repeatedly told him to slow down.

By comparison, Mr. Busch’s opponent in the case, Howard E. King of the firm King, Holmes, Paterno & Berliner, is a consummate industry insider, with an affable and sometimes sarcastic approach. In a sign of how familiar he was in the courtroom, Judge Kronstadt at one point joked that Mr. King need not worry about wearing a jacket the next morning because the jurors would not be able to see him as they entered through a side door.

Janis Gaye, the former wife of Marvin Gaye, said Mr. Busch’s distance from the center of the industry was one of the reasons that she and her children had hired him.

“He’s not one of the Hollywood mover-and-shaker guys who shows up at every party and says, ‘Hey, here’s my business card,’ ” Ms. Gaye said. “I’ve never met anyone like Richard Busch, and that’s fine with me.”