Music compositions*, like other forms of creative expression, are protected by copyright under the law.
Disputes over music copyrights are very common, but often don't go to trial.
In the event of a trial, the person claiming infringement (the plaintiff) has to prove two things: "access" and "substantial similarity."
Substantial similarity is a question of whether or not the average listener can tell that one song has been copied from the other. This is the "ordinary observer test," what Fakler calls "the hallmark of copyright infringement." The more elements two works have in common, the more likely they are to be ruled substantially similar. Proving substantial similarity in music cases is complicated by the fact that all songs carry two kinds of copyright, for composition and sound recording, that have to be evaluated independently.
"When people usually encounter a song they encounter it as a sound recording, and there are a lot of creative decisions the performer made in that recording that have added to what was on the page," Fakler said. "So a juror might hear similarities between two songs that are actually just similarities in the performances, not in the songs as written by the songwriter."
To avoid this problem, the judge on the "Blurred Lines" case ordered that only stripped-down tracks, restricted to disputed elements of the original compositions, could be played in court.
Though barred from playing "Blurred Lines," Thicke took to the witness stand with a keyboard and played other compositions, while dancing in his seat, to demonstrate how many songs, including Michael Jackson's "Man in the Mirror" and The Beatles' "Let It Be," share certain elements in common. The tactic echoed a similar move by John Fogerty in the famous case of Fogerty v. Fantasy, in which the Credence Clearwater Revival singer-songwriter was accused of plagiarizing himself. (A song that Fogerty wrote as a solo artist, "The Old Man Down the Road," was alleged by his old record label to infringe on a song he had written as a member of CCR, "Run Through the Jungle.")
Fogerty won over the jury by bringing his guitar to the witness stand and personally demonstrating why the two songs were different.
"I'm always kind of amused that judges let that sort of thing happen in court, because you can really manipulate the song when you're a performer," said Fakler. "To a certain degree, it's like O.J. Simpson with the glove."