Marvin Gaye's family sues Robin Thicke over "Blurred Lines"

(CBS News) Robin Thicke's "Blurred Lines" was perhaps this year's song of the summer. It was number one for 12 weeks in a row, selling more than six million digital copies.

However, the family of music legend Marvin Gaye says Thicke did more than blur the lines of borrowing a hook -- he stole it. In a lawsuit the family said "Blurred Lines" is a blatant rip-off of Marvin Gaye's "Got to Give It Up."

"If you listen to the music, I'm sure anyone will see the similarities clearly," said Gaye's son, Marvin Gaye III. "That's caused my family a lot of duress, and myself, also."

Thicke went to court in August asking a judge to stop the Gaye family from implying that "Blurred Lines" was stolen from Gaye. Now the family is formally claiming copyright infringement, usually proved by making direct comparisons of the written music itself.

But the Gaye family is taking it one step further, saying "the shared departures from convention, such as the unusual cowbell, instrumentation, omission of guitar, and use of male falsetto, all contribute further to the finding of substantial similarity here."

Music industry attorney Doug Mark told CBS News' Ben Tracy he's not convinced that it violates the copyright.

"I hear 'Blurred Lines' and I absolutely hear 'Got to Give it Up,'" he said. "But, are there substantially similar compositional elements to the two songs? It's sorta like, it may be a rip-off, but not a copyright infringement."

Thicke has said he's a Gaye fan and even that he was inspired by "Got to Give It Up." In May, he told GQ magazine "[co-writer] Pharrell [Williams] and I were in the studio and I told him that one of my favorite songs of all time was Marvin Gaye's 'Got to Give It Up.' I was like, 'Damn, we should make something like that, something with that groove.'"

But four months later, Thicke backtracked when threatened with legal action. A TMZ cameraman asked the singer if he thought of Gaye when he wrote the music; Thicke simply said, "No."

If Thicke is guilty of imitation, Gaye's family apparently does not find it flattering.

To hear a performance of "Blurred Lines," click on the video player below.

To hear a performance of "Got to Give It Up," click on the video player below.