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Now the producer has opened up about the creation of the song, revealing Mars was instrumental in marshalling the musicians in the studio and acting as a sounding board for Ronson as the track developed.

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"The song wouldn't have been as good if not for Bruno. I think people think I made Uptown Funk and sent it to Bruno to do the vocal. But that song is very much his creation. I remember spending three days in Memphis slaving over that song and thinking that we finally had it. I then got a call from him two days later saying, 'No, it's not it.' And I knew deep down it wasn't it either."

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