Sitting in a courtroom in June 2016, Bloomberg journalist Vernon Silver saw something that shocked him. A lawyer pointed out that Jimmy Page’s introductory guitar solo in Led Zeppelin’s “Stairway to Heaven” was not included in physical sheet music submitted to the U.S. Copyright Office.

“That moment in the courtroom was like somebody dropped a bunch of $100 bills,” Vernon told Marketplace host Kai Ryssdal. As Vernon recently reported in a piece for Bloomberg Businessweek, copyright protection based on deposited sheet music means pieces of pre-1978 classics like “Born to Run,” Hotel California” and “Stairway to Heaven” might up for grabs.

Click the audio player above to hear the conversation.