Any number of people in the music industry will claim that they know a hit when they hear one, but not Andrew Watt, who co-wrote two of the ubiquitous songs of summer: “Señorita,” Camila Cabello’s collab with Shawn Mendes (which has racked up 112 million streams just in the U.S.), and “Call You Mine,” the Chainsmokers’ banger with Bebe Rexha (which has accumulated over 175 million global streams to date).

“Anyone that says, ‘I knew it was a smash!’ — they don’t know what the f— they’re talking about,” says Watt, who was named producer of the year at 2018’s iHeartRadio Music Awards. “You just gotta make shit that you think is great and then hopefully the world loves it; that’s the greatest feeling. If you make music for any other reason,” he warns, “you’re gonna fall short.”

He admits he rarely falls short of being excited about his own creations — at least on day one. “Oh my God, every song I make, I’m so excited about it in the first 24 hours because I love music so much,” Watt says. He may not be able to predict the smashes but at least he’s found a way to weed out the B-sides: the Day 2 Test. “If I still really like the song 48 hours later, then I’ll take it as far as I can.”

His creative process in a nutshell? “The one consistent thing is that I’m always writing with a guitar in my hands. The guitar is like an extension of me,” Watt says. “I play to write, but I love to jam, too, so I would call myself a musician first and a producer/songwriter second. I’ll start by coming up with a riff or a progression with chords. Then I’ll think of a melody in my head.” The second constant is longtime collaborator Ali Tamposi, who was celebrated as songwriter of the year at the 2019 BMI Pop Music Awards. “I try and wait for my collaborators to do the toplines and vocals,” he says. “Whenever I collaborate with someone, it always comes out better.”

But in the case of “Señorita” and “Call You Mine,” Watt and Tamposi worked with artists who are acclaimed songwriters themselves, which means that there were a lot of cooks in the kitchen. And the artist is always top chef. “When there is an artist in the room, they are the gatekeeper in terms of what they want to say or not say, and then we all collaborate on melodies and lyrics,” he says. “It’s literally: May the best melody or the best line win.”

Watt is quick to point out that the end result is determined by factors that are much bigger than the songwriters — and even the artists. “It takes an army to make a hit song; that’s something people don’t realize,” he says. “How many great songs have you heard and you’ve been like, ‘How is this not a hit?’ It’s not just about that. It’s about the the labels doing the right things, the people marketing it, promo, the Spotify impact at the right time, what’s going on in culture, what’s going on in the artists’ lives, how people are reacting to them. You know, the song is the song, but artists are the vehicle. And if they’re not getting it right, then it doesn’t take off. So we are only as good as our collaborators.”

Fortunately for Watt, Shawn Mendes and Camila Cabello proved to be the perfect vehicle and they’ve driven “Senorita” straight to the top of the charts. (The fact that they used their personal lives — and a widely-reported romance — for fuel certainly helped.) That song, he recalls, began as a riff, and on that particular day he had bossa nova on the brain. “It was very ‘Girl from Ipanema’-ish,” says the man who also helped to craft “Havana” for Cabello. “I love Spanish-sounding guitar, so I had this riff and then a rough idea of chorus came out. Immediately I called Shawn and I was like, ‘I started this thing, you have to help me finish it.'” After taking a listen, Mendes shared some thoughts of his own. But unquestionably, the best idea he brought to the table was calling Camila.

These days the tabloids claim that Mendes and Cabello are joined at the hip, but the reality is that uniting these two was no easy feat at first. “It took a really long time for everyone’s schedules to get set,” Watt says, estimating that the entire process took as over a year, in fact. “We went back and forth, piece by piece, and eventually everyone got in the same room and put it all together.”

In retrospect, it proved to be worth the wait. “Shawn crushed it, man,” says Watt. “And Camila wrote incredible things. One of the most coveted lines is ‘You say we’re just friends, but friends don’t know the way you taste.’ That was such like a Camila moment. I’ll never forget when she spit that out. So, you know, sometimes songs are written in 15 minutes, and sometimes you take your time crafting them and create many different versions. They start from a really basic idea and turn into a shebang.”

“What I like about the production is that it’s simple and very vocal heavy,” Watt says. “The song is kind of love story — it’s a ‘West Side Story’ type of song about a guy and a girl.” Well, not just any guy and any girl — in this case the line between seductive duet and real-life romance has been blurred. “There’s real history there between the two of them,” admits Wattman. “They sing with so much emotion. When they’re singing, it doesn’t feel like they’re in competition. Their voices were meant to sing together. It’s such a cool moment.”

And musical moments that move the needle, not simply songs, are what Watt aims to make happen. “I love to create moments,” he says. “You know, I’ve had been blessed to have made a bunch of records where people collaborate with each other. And that seems to be something that people really dig — when two great forces come together.”

Of course, there is a flip side to working with two major forces in the entertainment industry. When creative differences inevitably ensue, the producer has to play peacemaker. And as it turns out, Mendes and Cabello were not always in perfect harmony. “Shawn and Camila are really powerful, strong artists, and it took a lot to get [them] on the same page creatively,” says Watt. “It was a lot of work,” he reiterates. “So I’m just happy that the song is out,” he says with a laugh. “And I’m proud that we pulled it off.”