Months ago, Dave Grohl teased some of the collaborations on the forthcoming Fooeys album Concrete and Gold, saying that one of them was the biggest pop star in the world. People guessed at Adele or Taylor Swift, but most slept on the actual biggest pop star in the world – JT.

In a new Rolling Stone interview, Grohl explains the singer visited the studio one day, and struck up a friendship with Grohl.

“We’d drink whiskey in the parking lot,” Grohl says. “He was really, really cool. Then the night before his last day, he says, ‘Can I sing on your record? I don’t want to push it, but – I just want to be able to tell my friends.’ ”

Timberlake then sang some backing ‘la’s’ on a track, and did well, from all reports. “He nailed it,” Grohl jokes. “I’m telling you – the guy’s going somewhere.”

Concrete and Gold will be out September 15.