There was much harmony along with a few discordant notes Monday as an en banc panel of the U.S. Court of Appeals for the Ninth Circuit took up the copyright case involving Led Zeppelin’s “Stairway to Heaven.”

All the judges who spoke during Skidmore v. Led Zeppelin seemed to agree that sheet music deposited with the Copyright Office, not sound recordings, define the scope of copyright for musical works governed by the 1909 Copyright Act. That prompted bitter protests from Francis Malofiy, the attorney representing the estate of Randy Wolfe, which alleges that Led Zeppelin copied Wolfe’s 1967 song “Taurus” when the group wrote Stairway to Heaven.