Why is this song so universally adored? Songwriter and producer Mark Ronson told us he has no idea. But he does know the story of how "Uptown Funk" came to be.

"[The song] came from an idea that Jeff Bhasker (producer for fun., Kanye West), who produced my record with me and wrote the album-we went over to Bruno [Mars]'s studio one night," Ronson recalls. "We had worked on 'Locked Out of Heaven' and 'Gorilla' together with Bruno and Phil [Lawrence, composer]. I don't remember how it started exactly. We had this other idea we were kicking around that I thought was cool but we just hit a brick wall with it. We started jamming."

This jam wasn't your average waste of time fishing expedition for ideas, Ronson says. First Mars got on the drums and began pounding out a straight beat. Bhasker, who Ronson calls "an amazing keyboard player" got on the synths and his Juno keyboard. Ronson was on bass. And the "Uptown Funk" groove kind of worked itself out. The guys got the basic groove of the song, recording about an hour of themselves playing the music and listening to it on a loop to come up with melody and lyrics. They wrote the first verse then. It was all they would get done for some time.