During his Music News interview, Ed detailed how x’s lead single, “Sing,” came about and what it meant to him:

Well, originally [Pharrell Williams] tweeted “This Angels To Fly song is great” a while ago and then at the Grammys, I don’t think he knew what I looked like, so I just went up to him and said, “I’m a massive fan, I just wanted to say that’s my tune!”, and then we swapped numbers.

“Sing” was from my first session with him, and when you work with Pharrell, he tends to push you: he wants you to do the best thing possible. So you don’t necessarily go for the first thing he plays you. It must have been on the seventeenth thing that he played me, and I had just dismissed everything. I just didn’t really get it. I don’t really get jazz chords and Pharrell’s very jazzy! He played me the beat, and I instantly dismissed it, it’s not for me. OK, fair enough, move on, but I had a guitar in my hand, and I started playing that riff and he just looked at me and said, ‘Do you know what you’re doing, man?’ I was like, ‘No!’, and then he puts back on the song and I said, ‘Oh, OK, but I still don’t want to do it”, but just said, 'Man, just try it, it’s not going to kill you to try it!’

So he went off—he has three different studios in his building and has three different sessions going on at any one time—and I wrote the top line. He came back in, we pieced it all together, I wrote probably seven different verses and three different choruses and then we just picked the best ones and stuck them together.

https://twitter.com/edsheeran/status/471421076069556224