John Mayer had "hang ups" about recording a song with Katy Perry.
The pair - who have been dating since mid 2012 - collaborated on John's latest single, 'Who You Love', but he was initially unsure if it would be a good idea for them to be on the same track.
He told US radio station z100: "I had this idea that just sat around for a while and I thought, 'Maybe I'll finish it some day' and I played it for Don Was who was producing the record with me and he said, 'Get Katy to sing on it'.
"Now, he could say that because he doesn't have to worry about all the hang ups that I'd have to worry about." However, the guitarist didn't have to worry as Katy easily separated her personal and private lives when it came to recording her parts.
He added: "She was an artist in the studio and partner out of the studio. It was really professional. "There was a moment where she was like, Let me just go through it once', and the way I work is, 'Let's get this and that and that' and she was like, 'Let me try it my way.'
"We were just fine before we met each other, that's what we say - 'You were fine before I met you, you don't' need my advice,' and vice versa." Katy has said her recent single, 'Unconditionally', was written about John, as well as a life-changing trip she made to Africa.