Last month, Dave Grohl said that Foo Fighters' new record, Concrete and Gold, will feature vocals by “probably the biggest pop star in the world.” Now, in a new interview, he has cleared up speculation about who that guest star isn't.

"Neither Adele nor Taylor Swift sang on the record," he told Rolling Stone. He still would not reveal the singer's name.

Adele had been pegged as the favorite to be on the record, due to the fact that Concrete and Gold was produced by Greg Kurstin, who worked on her 25. The only confirmed guests so far are Bird and the Bee's Inara George, smooth jazz saxophonist Dave Koz, Alison Mosshart of the Kills and Shawn Stockman of Boyz II Men, who created a choir of himself with approximately 30 vocals tracks on the closing title song.

"When he left the room, I turned to everybody and said, 'The Boyz II Men dude just raised the f---ing bar,'" Grohl said. "'Every song has to be that big.'"

Grohl also discussed how his 2015 broken leg resulted in the band taking its hiatus. "In order to take care of myself, I needed to get away from everything," he said. "I was in physical therapy for two or three hours a day for almost a year." His original goal was to go a full year without making any music, but six months after telling Foo Fighters of his plan, he wrote "Run."

But in order to write the lyrics for the record, Grohl decided to isolate himself, renting an AirBnB in Ojai, Calif. "I brought a case of wine and sat there in my underwear with a microphone for about five days, just writing," he added. "It happened at the perfect time. I was inspired by what was going on with our country -- politically, personally, as a father, an American and a musician. There was a lot to write about."

Concrete and Gold arrives Sept. 15.

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