Deep in the archives of the Andy Warhol Museum, a lost piece of musical history has been discovered: A tape of unreleased recordings by Velvet Underground frontman Lou Reed with lyrics based on Andy Warhol’s 1975 book The Philosophy of Andy Warhol: From A to B and Back Again.

Judith Peraino, a Cornell music professor, discovered the cassette tape two years ago, while researching a book on Warhol in the 1970s. She has since published her findings in the new issue of the Journal of Musicology.

One of nearly 3,500 audiotapes in Warhol’s archives—the artist often recorded conversations for books, plays, or Interview magazine—the newly discovered tape contains 12 completed songs and parts of a 13th. Only a handful of the songs have ever been heard before.

“What makes this rare is the gift aspect of the tape—that Lou Reed intentionally created both a curated set of songs and a composed set of songs on tape meant only for Warhol.” Peraino told the Cornell Chronicle. “This is a harbinger of the mixtape culture and gift-giving that flourished in the 1980s and 1990s.”

Julian Schnabel, Lou Reed. Courtesy of the New York Public Library.

Reed is the only musician on the recording. “He sings softly and close to the microphone with a slight nasal voice and lisp,” Peraino wrote in the Journal of Musicology. “The chord changes are basic and repetitive, drawn from the vocabularies of folk music or rudimentary rock.”

Warhol managed the Velvet Underground in 1966 and ‘67, but Reed fired him before beginning work on the band’s second album. Nevertheless, the two artists remained friends, and were even considering collaborating on a Broadway play version of Reed’s album Berlin in 1974. But the project never came to fruition and Warhol instead produced the musical Man on the Moon, which bombed and closed after just five performances.

Peraino speculates that Reed’s tape based on Warhol’s Philosophy is related to their aborted project, but that it was recorded at a time that Reed was no longer interested in collaborating with Warhol. “I think he was making fun of the idea [of a musical], digging at Warhol,” she told the New York Times.

Lou Reed’s Philosophy tape, a previously unheard recording made for Andy Warhol.

Indeed, the recording includes some bitter words from Reed, in which he accuses Warhol of using people and claims it would have been better if the artist had died after being shot in 1968. After the song ends, Reed adds a spoken apology.

Due to copyright concerns, it’s unlikely that the public will hear the recording any time soon—only professional scholars have access to the archives, and even Peraino was prevented from quoting any of the lyrics directly. Both the Andy Warhol Foundation for the Visual Arts and the Reed estate could conceivably claim rights to the tape, as well as Reed’s record label at the time of the recording.