It has been three years since the Foo Fighters released Sonic Highways and now, we are nearly one month away until its follow-up arrives. Concrete and Gold will be released on September 15th via Roswell/RCA and it will feature quite a few special guests. The band have already announced Boyz II Men’s Shawn Stockman will appear on the title track and The Kills’ Alison Mosshart is featured in two songs, “La Dee Da” and “the Sky is a Neighborhood.” It wasn’t too long ago when Dave Grohl promised this album will include the biggest pop star in the world and now, he revealed one famous icon.

Grohl recently told ET Canada:

“Paul McCartney plays drums on one of our songs. He’s a pal. We’ve known him for a long. He’s great. He’s the most wonderful person in the world. He’s a great guy. He hadn’t even heard of the song. He comes in and Dave picked up an acoustic and showed him real quick. He sat on his special drum set that his tech set up for him. I sat there with a drumstick conducting. He did two takes.”

Grohl recently explained to Rolling Stone about the not-yet-revealed famous pop star who will be featured towards the end of the album on backup vocals:

“It was sort of towards the end of the album and this person came up and said, ‘Man, I’d really love to sing on your record.’ I looked at [producer] Greg [Kurstin] and said, ‘OK, come in tomorrow and we’ll figure something out.’ So we found a backup part for this person to sing and we decided we were gonna make it our own dirty little secret and see if anyone can figure it out.”

Our guess is, this mysterious pop artist would most likely be Lady Gaga. It is most likely her experience sharing the stage with Metallica influenced her to have more rock/metal collaborations.