Even in death, musical icon Prince is surprising fans. It’s been rumored that Prince’s Paisley Park compound in Minnesota contains an underground vault filled with unreleased tracks that would keep his legacy alive for over a century.

Now, those who have worked with the artist confirmed that the rumors are indeed true.

Prince’s longtime friend and sound engineer, David Rivkin said that much of the vault material has never been released.

"Maybe he instructed his lawyers to never release them. I hope that's not the case. I'd like to see some of them come out, a lot of them were pretty great," Rivkin told New York Daily News.

Susan Rogers, another sound engineer who worked with Prince, claims she was first to create the vault:

“I joined Prince in 1983 when he was preparing to do Purple Rain. I realized it would be smart for me to get his tapes together in one place. I was aware there were a lot of pieces missing. It became an obsession. I wanted us to have everything he’d ever recorded. I called up the studios he’d been using and said: ‘Have you got any Prince tapes’? This is his legacy. We need to protect these things. It’s an actual bank vault, with a thick door. It’s in the basement of Paisley Park. When I left in 87, it was nearly full. Row after row of everything we’d done. I can’t imagine what they’ve done since then."

Prince’s composer for 30 years, Brent Fischer, believes that over 70 percent of the music he worked on with the artist has yet to be released, according to The Independent.

“There are a lot of songs that were sent to us clearly with the idea that they would never be released. They were almost comical songs that he would work out with his horn players. There was a lot of wild horn parts and experimentation with samples. I’d like to see 'All My Dreams' come out. We enjoyed that song so much. I think it’s nine-and-a-half minutes. It’s this epic journey.”

Last year, investigative reporter Mobeen Azhar verified that the priceless vault exists in his documentary, “Hunting for Prince’s Vault.” He badgered the lawyers, managers, engineers and musicians at the Paisley Park recording studio for specifics about the extensive collection.

“He was recording all the time,” Azhar said. “One of [Prince’s bandmates] said, ‘If Prince was to leave the world today, he’s got enough unreleased music to put an album out every year for 100 years.’”