On 2 May 2016, the satire web site The Onion published an article claiming that Prince's music vault contained nothing but Billy Joel cover songs:
Ending rampant speculation regarding the extent of the late musician's catalogue of unreleased recordings, the executors of Prince's estate announced Monday that the performer's famed vault in his Paisley Park residence sadly contains 37,000 hours of Billy Joel covers. "Prince was constantly creating throughout his career, and after finally accessing his vast trove of previously unheard music, we now know that he produced over 40,000 albums' worth of material that is, unfortunately, made up entirely of songs originally recorded by Billy Joel," said attorney L. Londell McMillan, reluctantly admitting that Prince had produced at least 9,000 hours of "Uptown Girl" covers alone.
The Onion is a well-known humor and satire web site, but some people encountered the article on social media, where its source was not readily apparent.
While there is no truth to this story, the article (like most in The Onion) is at least based on real events. Prince reportedly had thousands of unreleased songs in a "vault" when he passed away. According to a report filed by ABCNews on 29 April 2016, the vault was drilled open and contains enough material to release an album every year for the next 100 years:
The seven-time Grammy Award winner reportedly left behind a vault containing so much music his estate could put out an album a year for the next century.
"We could put out more work in a month than most people could do in a year or more," Susan Rogers, Prince's former recording engineer, told ABC's "Good Morning America."
Rogers added that the vault in Prince's Paisley Park home was a giant room with shelves that filled up quickly. The door to the vault was sealed with a large spinning wheel.
As of 2 May 2016, exactly what music Prince's vault contains is still unknown. We do know, however, that the claim that Prince's music vault was full of nothing but Billy Joel cover songs originated with a humorous and satirical web site, and it would be extremely surprising if it turned out to be true.