Foo Fighters' new album Concrete and Gold features an unlikely collaboration with Boyz II Men's Shawn Stockman.

The rockers previously revealed they'd roped in popstars to record vocals on the album at Los Angeles' EastWest Studios, but had remained tight-lipped about the identity of those involved.

Asked by BBC radio presenter Matt Everitt what was the weirdest moment the band experienced making the record, frontman Dave Grohl said, "The guy from Boyz II Men walking through the parking lot and me saying, 'Oh dude, will you sing on our record?' And he does. On the heaviest song on the entire record. It sounds like if (Black) Sabbath and Pink Floyd made their... It's the last song on the record, with the guy from Boyz II Men, his name's Shawn, singing and it's like 40 vocals stacked."

Drummer Taylor Hawkins explained that the band have wanted to move away from their rock roots on an album for a while, but had always ended up sticking to the genre.

"Every time we start a record Dave goes maybe we really need to get weird on this record," he recalled. "And then we always pull back and go 'let's just make a good rock 'n' roll record and... I think we got weird’."

One star rumoured to appear on Concrete and Gold is British soul superstar Adele, and Dave has previously teased a whole host of A-listers could be taking part.

"You might have Shania Twain having a record-release party, or the guy from Deep Purple hanging out with Jason Bonham, or Justin Timberlake would be in for a couple of weeks, or Lady Gaga working with these other cats from Nashville," he said. "And every so often we'd be like, 'Hey, wanna come sing some backing vocals?' and they'd just f**king do it."

Concrete and Gold hits shelves in September (17).