Jay Z was only granted permission to sample The Doors' song Five To One on his 2001 rap classic The Blueprint after personally writing a letter to drummer John Densmore arguing his case.

The legendary rocker admits he was initially unsure about the project when the 99 Problems hitmaker first contacted him because he didn't really understand what hip-hop music was.

During an interview on Huffington Post Live, he says, "I was like, 'What is this stuff? There's no melody.' I was a curmudgeon."

Jay Z caught wind of Densmore's objections and immediately reached out to the musician by penning a note explaining exactly why he wanted to sample the track for Takeover.

Densmore adds, "Jay Z wrote me a letter saying, 'Hey, we're fighting the authority just like you guys did back then.'"

The rap mogul also sent him a T-shirt featuring the logo of Def Jam Records, the label Jay Z served as president of at the time - and the piece of clothing actually came in handy for Densmore years later while writing his new book, The Doors: Unhinged.

The rocker reveals he turned to Jay Z to give him some words about success and used lyrics from Jay Z's book Decoded.

He continues, "I took a photo of me in this T-shirt, which I saved, and sent it to him and said, 'Hey, would you give me some of these words for this (the book)?'"