Tonight, new controversy as a pop star defends his hit single by saying, he didn't really write it, and that he was drunk and high the whole time anyway. Believe it or not, that's part of the legal... See More
Tonight, new controversy as a pop star defends his hit single by saying, he didn't really write it, and that he was drunk and high the whole time anyway. Believe it or not, that's part of the legal defense presented by robin Thicke. Now being accused of ripping off Marvin Gaye. Many artists admit they borrow from the greats. But is this straight up stealing? Here's ABC's Rebecca Jarvis. ? Everybody get up ? Reporter: Robin Thicke's "Blurred lines," first controversial for its provocative video is now at the center of a lawsuit over whether the singer and producer ripped off Marvin gape's 1977 hit "Got to give it up." Heard here on "Soul train." Take a listen for yourself. ? Hey hey hey ? ? Reporter: Thicke was quick to name gay as the inspiration in several interviews, including this one on VH1. We went in the studio and I had mentioned to him that one of my favorite songs was "Got to give it up." We tried to get a little groove like that going. We really wrote the whole song in about a half an hour. Reporter: And Marvin Gaye's family seemed to agree in this interview on "Et." First thing I thought of was one of my dad's songs and I thought it was a remix. But it wasn't. Reporter: A law suit was filed against Thicke and pharrell. In newly released depositions, Thicke claims he was drunk in every interview he gave about the inspiration behind "Blurred lines." I had a drug and alcohol problem for the year and I didn't do a sober interview. Every day I woke up, ill would take a vicodin to start the day. Responding to the release of the deposition, Thicke's lawyer telling a B bc news, robin's moment of personal veler inability is being exploited in the hope of diverting attention from the obvious weakness of their legal claim. According to pharrell's deposition, Thicke played almost no part in creating "Blurred lines." It was 80% completed by the time he showed up to the studio, late. Thank you, guys. Reporter: If he could have transported himself there while ill was making the track, you would have something to go on. But he wasn't there, sir. He wasn't there. All this, just the latest salvo in the Patel of plaguer rich in pop music. Some of music's greats have been akudzed of stealing. Johnny cash's infamous song cost him $75,000 for borrowing the melody from the lesser known. ? I hear the train coming ? ? it's rolling around the bend ? ? I ain't seen the sunshine ? ? since I don't know when ? Reporter: John Lennon settled out of court for the beatles song "Come together. " It's beat and similar break structure echoed chuck berry's "You can't catch me." ? I bought a brand new ? ? something strange in the neighborhood ? ? who you gonna call ? ? ghostbusters ? Reporter: Ray parker's "Gho "Ghostbusters" theme song, nominated for an Oscar, earned him a lawsuit from Huey Louis for its striking resemblance to "I want a new drug." ? I want a new drug ? ? one that does what it should ? ? one that won't make me feel too bad ? ? one that won't make me feel too good ? Reporter: Eventually they settled out of court. But the stakes could be even higher for "Blurred lines." The album following a hit single sold some 175,000 copies in its first week. Sold about three quarters of a million to date. Reporter: Marvin Gaye's family stands to win a percentage of those sales. Whatever the outcome, we decided to take the two songs to a professional. New York City music producer and instructor, Chris petty. Check it out. This is the original one. And what I've done is, I cued it up to the parts where it started, so -- Reporter: Marvin Gaye. This is the Marvin Gaye version. ? and here's what the beginning of "Blurred lines" sounds like. ? Reporter: And this is the heart of the argument. You would have thought it was "Blurred lines." Reporter: But Thicke's camp says being reminiscence of a sound is not copyright infringement. And pharrell argues similarities in sound are just a coincidence. I see when people say they feel that. I understand that. But the truth of the matter is, silk and rayon are two different things. They just feel the same. Katy Perry's hit "Roar" reminded fans of the hit "Brave." ? You can be amazing ? Reporter: No lawsuit there. And lady gaga's "Born this way" echoed Madonna's "Express yourself." ? You'll go far ? ? when you're not there ? Reporter: Attracting attention, but not legal action from the queen of pop. It feels reduckive. Reporter: When you know something is tried and true, it's been successful in the past, does that mean it's smart to try -- What I've heard with a lot of the early hip hop producers, taking a song that was popular and giving rebirth to it and everything by bringing it into something modern, but what is it that people are really attracted to with the new song? Reporter: Which seems impossible to define. Which seems impossible to define, yeah. ? You're a good girl ? Reporter: The fate of "Blurred lines" is now up to the courts. Pharrell and Thicke argue that since the gayes own just the come me situation and not the recording, the judge must decide by only considering the composition and not other elements, like the instruments involved. Marvin day's son told "Et" that the lawsuit had one main objective. I want to see my father get credit for his work. Reporter: But according to pharrell's attorney, Marvin Gaye's family smelled money and rushed to make their infrin infringement demand. Regardless of the legal outcome, this case could have a chilling impact on the already troubled music industry. Everyone is going to think twils twice before they jump on a track that has a marked similarity to another track. The next time someone's in a studio and plays a track for a singer that sounds like something else, people are going to stop and say, well -- I like the way that sounds, is it a little too "Blurred lines?" Reporter: It's scheduled to go to trial next February. For "Nightline," I'm Rebecca Jarvis in New York.
This transcript has been automatically generated and may not be 100% accurate.