Tom Petty, Sam Smith and the History of Music Legal Battles

When you heard Sam Smith’s hit "Stay With Me,” you might have noticed that the melody is similar to Tom Petty’s “I Won't Back Down." Tom Petty thought so, too. This week we learned that the two artists have agreed to share royalties from the Sam Smith song. This isn’t the first time an artist has been inspired -- maybe a little too inspired -- by another artist. Even as we speak, representatives of the band Jimmy Eat World are reportedly talking to Kelly Clarkson’s people about the similarity of their biggest hit to her new single. What’s the legal standard for songwriting plagiarism, and what are some of the most famous cases in history?