I am a big fan of the Russian Classical composer Sergei Rachmaninoff. Eric Carmen used the melodies from two of Rachmaninoff’s most famous pieces. “All By Myself” used the 2nd movement from Rachmaninoff’s 2nd Piano Concerto and “Never Gonna Fall in Love Again” used the theme from the adagio movement of Rachmaninoff’s 2nd Symphony. Carmen had training in Classical music. He thought the pieces were in the public domain but they were not and the Rachmaninoff estate sued Eric. He ended up writing a check.
No music lawsuit is stupider than Mike Batt settling for a six figure sum to the publishers of John Cage’s 4’33”.
As great as Led Zeppelin is, they were the kings of plagiarism.