Pharrell and Robin Thicke's "Blurred Lines" was one of the biggest songs of 2013, and as 2017 approaches, the two musicians continue to defend the song in court against a copyright suit filed by Marvin Gaye's family. In August, Pharrell and Thicke appealed a court decision that ruled in favor of Gaye’s estate, ordering them to pay $5.3 million and 50 percent of all songwriting and publishing revenues.

Now, according to The Hollywood Reporter, Gaye's estate has challenged the appeal in court Thursday (Dec. 22). "This case stands for no more and no less than the fact that the original work of an artist may not be appropriated without consent and fair compensation" a brief filed yesterday reads.

The debate centers on the difference between musical inspiration and unlawful copying with the strength of the copyright claim being called into question.

"A music copyright is not 'thin,'" the brief states. "Music is imaginative, not strictly factual or functional. ... Not surprisingly, the Thicke Parties fail to cite a single case applying the virtual identify doctrine to an original musical work."

Until 1978, the U.S. Copyright Office would only accept written submissions, Gaye's "Got to Give It Up" recording, the source material said to be used, rejected by the office. That led to a debate over admissible evidence which has in part helped to draw the proceedings out even further.

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