The Flames.

The Case: Courts found that two tracks on II, Led Zeppelin's sophomore album, owed crushing debts to Chicago blues classics by Willie Dixon. Album opener "Whole Lotta Love" copped lyrics from the 1962 Dixon-penned Muddy Waters song "You Need Love." The source material for Zep's "Bring It On Home" is even more apparent. Page borrowed the intro and outro of Sonny Boy Williamson's 1966 original, intending it as a deliberate homage to the blues great; Dixon didn't see it that way and sued the band for copyright infringement in 1972. He took them to court again in 1985 over writing credits on "Whole Lotta Love," which by then had become a classic-rock staple.

The Verdict: Both suits were settled out of court for undisclosed – but presumably large – sums. Songwriting credit reverted to Dixon in the case of "Bring It On Home," and his name is also included on "Whole Lotta Love" along with the rest of Led Zeppelin. Despite the cost, Robert Plant was unbothered by the controversy over the latter song. "Page's riff was Page's riff," he told Musician Magazine in 1990. "It was there before anything else. … At the time, there was a lot of conversation about what to do. It was decided that it was so far away in time and influence that … well, you only get caught when you're successful. That's the game."

Why It Matters: Led Zeppelin's artistic debt to the blues, one shared by many of their British classic-rock peers, was never in doubt, but these suits actually took legal stock of that debt – and put a price tag on it.