Dave Grohl and Justin Timberlake during Spike TV Presents 2003 GQ Men of the Year Awards - After Party at The Regent Wall Str
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Foo Fighters' upcoming album Concrete and Gold is filled with tons of special features, but the latest reveal may be one of the most unexpected. Frontman Dave Grohl revealed Justin Timberlake is the “the biggest pop star in the world” he was previously teasing on the new LP.

Grohl recalled how things went down in Rolling Stone's new cover story (a little bit of liquor helped the two bros come together):

“Then there was the day Justin Timberlake dropped by. He listened to what the Foos were doing and liked what he heard, and pretty soon he and Grohl were hanging out regularly. ‘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.’ So the band had him add some ‘la la la’s’ to one track. ‘He nailed it,’ Grohl says. ‘I’m telling you – the guy’s going somewhere.'”

Grohl's other famous buddy Paul McCartney, who he calls the most exciting guest, also appears on the new album. "He was so fucking good. We played for an hour, then took a break and had bagels and tea, he told RS after Macca only recorded two takes. "I thought we were done—I didn't want to rag him out—so I was out having a cig, and someone goes, 'Hey, Paul wants to jam some more.' He rounded everybody up, and we jammed for hours: 'Let's write some songs, man!' "

Concrete And Gold, Foo Fighters' ninth album, is set to be released Sept. 15. The follow-up to 2014's Sonic Highways will also feature artists like Boyz II Men member Shawn Stockman and The Kills' Alison Mosshart. Next, watch this classic Fuse interview where Dave Grohl reflects on his musical upbringing: