How did you come to write Shallow with Lady Gaga, Mark Ronson and Andrew Wyatt?

I met Mark through Amy [Winehouse]; we first hung out at MGMT’s debut show in London. We used to jam all the time and I wound up working with Mark and Andrew on a couple of songs for [Ronson’s 2010 album Record Collection]. To watch a song go from my guitar to the finished product was a new and incredible alchemy. I was giving Gaga guitar lessons around the time we wrote Shallow. We really got on; there’s something very familiar with her. You can’t A&R a song like Shallow. It’s 10 years of relationships boiled down.

Had you seen A Star Is Born when you started writing the song?

The film was just a script when we started, an unfinished script.

What were the songwriting sessions like?

It felt so organic to be in that circle; Gaga at the piano, me and Andrew with guitars, and Mark pacing around like a captain making sure we didn’t start making jokes about Muppets or whatever. It was almost like ping-pong: Andrew would have a little melody and she’d have a lyric and everyone would nod. We’d bang chords back and forth to see what felt right to the ear, and she’d do them on the piano. The song came to us on a broken wing, and because the four of us had a relationship and experience we were able to mend it and let it fly. And if all four of us hadn’t been there I don’t know if there would have been the strength to do that and put it into the world.

Were there any parts that were tricky?

The bridge seemed long at the time but they shortened it. The “sha-la-la”s when we were first doing them were more like the Ronettes, but I think that was because we were over-excited. So we had to rejig them.

Is there a part of the song you are particularly proud of?

Gaga’s verse. When you’re working with someone who comes around once in a generation, you want to facilitate and support and get that song out of the room and put as much wind behind her sails as possible. Every day, I try and write a little list of things I am grateful for and I can put that collaboration and working with her at the top of the list.

What has happened since the song came out?

It’s really, really fun. I don’t really maintain a public profile [any more] so to be on stage in front of millions of people jogged a lot of memories. Professionally it’s been fun, too. Linda Perry walked up to me at the Critics’ Choice awards and gave me her number. I spent the first hour after the Golden Globes in shock. Even Gaga was like: “Holy Shit! Can you believe we did this in four hours!?”