The subject of Carly Simon’s “You’re So Vain” is one of the greatest mysteries of modern music , but in a new interview with PEOPLE about her forthcoming book Boys In the Trees, the legendary singer reveals who the iconic track is about … sort of.

According to Simon, only the second verse is about Warren Beatty. “I have confirmed that the second verse is Warren,” she tells PEOPLE. “Warren thinks the whole thing is about him!”

That verse in question has these lyrics: “You had me several years ago when I was still quite naive/ Well you said that we made such a pretty pair / And that you would never leave/ But you gave away the things you loved and one of them was me/ I had some dreams, they were clouds in my coffee.”

Simon acknowledged Beatty may have been one of the inspirations for the song back in a 1989 interview with Fame Magazine, but she denied for years that it was about one man. Many speculated that it was about Beatty, Kris Kristofferson, David Cassidy, or David Bowie.

Beatty, though, has long thought “You’re So Vain” was about him, and said in a 1999 interview, “Let’s be honest, that song is about me.”

Simon says the other verses are about two different men, but she wouldn’t say who, and doesn’t think she’ll reveal their identities anytime soon. “At least until they know it’s them,” she says.