NEW YORK • There was no pressure. It was just another day in the recording studio.
That was the key to writing Ed Sheeran's Shape Of You, which has been on the Hot 100 since it was released on Jan 6 and topped Billboard's year-end singles chart.
It is a tale of romance sketched in mundane details - "now my bedsheets smell of you" - with four chords delivered in plinking, dancehall-tinged syncopation.
The song has drawn more than 2.8 billion views on YouTube and is also the most-played track on Spotify - with more than 1.5 billion streams.
Sheeran thought he already had enough songs for the album he released this year and he was pondering the final selections.
As a diversion, he set up a recording session for his sideline: supplying songs to other performers.
"I didn't make this song to be mine to sing," he said.
A singer he had been touring with, Anne-Marie, directed him to producer Steve Mac, a longtime British hitmaker who has worked with singer Susan Boyle and Irish boyband Westlife, among many others. Mac co-wrote Westlife's Flying Without Wings, which, Sheeran said, is "one of my favourite songs of all time".
Sheeran also invited a long-time friend with whom he has written hundreds of songs, Johnny McDaid, a member of Snow Patrol, to the session at Mac's Rokstone Studios in West London.
Like many current pop hits, Shape Of You was written in a brainstorming session where ideas are developed or discarded fast, with computers and instruments close at hand and recorders running. "The best songs that I've ever written, I don't really remember writing," Sheeran said. "They take like 20 minutes and then they're just done."
Fifteen minutes after he met Mac in the studio, Shape Of You was underway. Mac came up with the core keyboard riff, playing it with the log-drum sound that happened to be on his synthesizer at the time, hinting at a Caribbean-flavoured beat that was already popular.
Sheeran plays his concerts solo with a looping device, performing and then layering all the parts live; he writes songs the same way, stacking and nesting motifs. Mac was surprised to find that Sheeran did not need to hear what he had already constructed.
"He's not actually layering over the top," Mac said. "He's doing one part, then he does the next part, then he does the next part. And then he says, 'Put all of those on top of each other.'"
The vocal lines also bounced against the beat, adding more syncopation "like a mantra", McDaid said. "Like a heartbeat that happens inside it."
The song was taking on a rhythm-and-blues feel; Sheeran started thinking of it as something for a female harmony group or maybe Rihanna. As they were working, the collaborators realised that the emerging chorus melody resembled TLC's 1999 hit No Scrubs. Sheeran said negotiations to add credit for the songwriters of No Scrubs - Kandi Burruss, Tameka Cottle and Kevin Briggs - began well before the song was released.
The melodies started out as wordless syllables. But Sheeran's diaristic side emerged in the first verse: "All the people I know that have met people in pubs, and actually had a conversation, have ended up in long relationships," he said.
He also came up with what he thought would be a good phrase for a chorus: "I'm in love with your body."
Mac and McDaid were not convinced. "'I'm in love with your body', on its own with no addendum, with nothing at the end or no preface, felt objectifying to me," McDaid said.
He said "the shape of you", a phrase common in Northern Ireland, where he is from, "can say 'whatever you are, whatever it is, I'm in love with you'. You know, it's the shape of who you are figuratively".
After about 90 minutes, they had recorded the complete song. "It was the best hour-and-a-half of my life," Mac said.
They wrote four more tracks that day, destined for other acts: Liam Payne, DJ Snake, a duet for Faith Hill and Tim McGraw.
Sheeran thought Shape Of You was "fun" and it might be good for Rudimental, the band who, like him, are on the Atlantic label. He played it for Atlantic UK president Ben Cook. And he got a fateful response. "He was kind of just looking at me," Sheeran said. "Like, 'Why do you want to give this away?'"