It is one of rock’s most famously fraught relationships: Lou Reed and Andy Warhol, who managed Reed’s groundbreaking 1960s band, the Velvet Underground, for a couple of years before an acrimonious split. Warhol’s ideas on art, pop culture and hard work loomed over Reed for the rest of his career, though the two never worked together again.

But a decades-old cassette tape, uncovered in Warhol’s archive, suggests a path untaken: a suite of songs by Reed based on snippets from his mentor’s 1975 book, “The Philosophy of Andy Warhol: From A to B and Back Again,” which may have been connected to loose plans the two made to collaborate on a stage musical.

The tape, recorded in 1975, was found by Judith A. Peraino, a Cornell music professor, who said she stumbled across it two years ago at the Andy Warhol Museum in Pittsburgh while researching a book about Warhol in the ’70s.

As Peraino writes in The Journal of Musicology, Side 1 of the tape has live recordings that Reed put together from his 1975 tours , with songs from his albums “Sally Can’t Dance” (1974) and “Coney Island Baby” (1976). But Side 2 — labeled “Philosophy Songs (From A to B & Back)” in scrawled black ink — contains 12 songs, and a fragment of a 13th, that have never been released, and were largely unknown.