JLS and Rochelle in the studio

JLS and Rochelle from The Saturdays have been recording together, but it's not a collaboration.

JLS have confirmed that Rochelle, Marvin's girlfriend and member of The Saturdays, has been in the studio with them to test out vocals for a female part in one of their upcoming tracks.

Rochelle says she was happy to help out but won't be singing on the same track as her boyfriend as they boys already have someone lined up...

Marvin told Star magazine: "She does help out. We've got an idea for a duet with a female star but we can't say who yet. When we had written the girl part, Rochelle came in and helped out and laid down the vocals for it."

"She did really well but we know who we want and it does look like it's going to happen."

Who do you think it could be? Who would you like it to be?