In June (14), Simpson revealed he has spent time with the Baby hitmaker in a recording studio but he gave no further details of the collaboration.
Now he has opened up about the project, telling the Sydney Daily Telegraph the pair has an album of joint tracks ready for release in November (14).
Simpson says, "It is a smack bang duets (album). Justin has been a good mate of mine for a while. It's just us writing. He told me he felt like I'd figured myself out and have grown into what he knows I will be, so he was like, 'I see you as that guitarist, singer-songwriter you've always wanted to be'. I play all the guitars on the album."