Many of Shawn Mendes' biggest hits have one thing in common: the songwriting team.

Over the course of his six-year career and three chart-topping albums, the Canadian pop star has gradually built himself a robust team of hit-makers that has delivered hits like "Stitches," "Treat You Better," "There's Nothing Holdin' Me Back" and "In My Blood." A quick scroll through the songs' credits will reveal some consistent names, but one of the most notable constants is Teddy Geiger, someone who probably understands Mendes' meteoric rise to fame more than anyone else.

Almost 10 years before Geiger — who was assigned male at birth but came out last year as a trans woman — joined forces with Mendes, she too was a pop star. In 2004, she appeared on the reality series In Search of the Partridge Family, where she competed for (and lost) the chance to be cast as Keith Partridge. The following year, she opened for Hilary Duff's summer tour. Her 2006 debut album, Underage Thinking, reached the Billboard 200 top 10 and singles "For You I Will (Confidence)" and "These Walls" earned her lots of airplay on MTV, MuchMusic and various radio stations. She was, at the time, considered a bona fide heartthrob.

But a frustration with the direction her career was headed — Geiger was pushed to act and pursue other projects that took her away from the creative side of music — soon pushed her to leave the music industry altogether. In 2009, she moved from Los Angeles back home to upstate New York.

"I started out as an artist, but I've always wanted to be a writer and producer," she now recalls. "One of the things that I loved about working on that first album was working with Billy Mann, who produced the album, and all the people who worked to finish it. Just seeing how they did things and learning. I've always loved the creative part of music more. That's what makes me happiest."  

Returning to the music industry

After some time at home, Geiger reset her sights on songwriting and producing and returned to Los Angeles. She "hit the ground running": Geiger signed a publishing deal and was quickly set up with an average of six sessions each week.

"Every day, I'd just wake up and meet new people," she says. Sessions can range from "sometimes great" to "sometimes horrible," but Geiger says it's all a matter of "finding a rhythm and finding my people." This time, instead of being the artist at the front and centre of it all, she would sit on the other side of the recording booth, helping a new crop of pop stars pen songs, including some early tracks for One Direction ("Little Black Dress," "Where Do Broken Hearts Go") and Drake Bell ("You're Not Thinking").

She first met Mendes in 2015 when he cut "Stitches," a song Geiger wrote with Danny Parker, and was sent by her publisher to Mendes' team. "We instantly just had a connection and I felt that he was super talented," Geiger remembers. In some ways, it's easy to see why the two would get along, musically. Geiger's solo work delivered sweet pop melodies through lots of acoustic guitars and stripped-down sincerity, which is the same vehicle Mendes uses to drive home his anthemic hits. That immediate kinship Geiger describes led to an invitation to collaborate more, particularly on Mendes' next album, 2016'sIlluminate.