How buzzy artist JP Saxe went from Julia Michaels’ ex to John Mayer’s opener

If there is such thing as a songwriter’s sixth sense, then JP Saxe certainly possessed it when he penned his Grammy-nominated hit “If the World Was Ending” with ex-girlfriend Julia Michaels in July 2019.

“I wrote a song inspired by an earthquake, and then six months later the world is ending,” said Saxe, 30, of the tune that proved to be an eerie foreshadowing of the global pandemic in 2020. “Like, you don’t really see that s—t coming.”

But that didn’t stop social media conspiracists from having other ideas. “It was a very bizarre time in my creative life to be accused on Twitter of having some sort of insider information,” said Saxe, whose initials stand for Jonathan Percy.

Still, he’s “extremely grateful” for the song that introduced him to the world. And having just dropped his second LP, “A Grey Area,” last Friday, the buzzy artist is making even more fans as he opens for his idol John Mayer on the fall leg of his solo acoustic tour that kicks off Oct. 3 at Madison Square Garden (with a second MSG show on Oct. 4).

It was a songwriting session with one early fan, “Issues” singer Michaels — who had shared Saxe’s song “25 in Barcelona” on Instagram — that jump-started his career as well as his love life. The two tunesmiths wrote both “If the World Was Ending” and Lewis Capaldi’s “Wish You the Best” on the very first day that they met.

Produced by Billie Eilish’s brother Finneas, “If the World Was Ending” was originally released as a duet between the songwriters-turned-sweethearts in October 2019. However, the tune took on another life with an all-star video — featuring everyone from Sam Smith and H.E.R. to Keith Urban and Alessia Cara — that benefitted Doctors Without Borders in the COVID-stricken spring of 2020.

Two years later, Saxe and Michael’s relationship came to its own ending in April 2022. But the Toronto native, who moved to Los Angeles when he was 19, doesn’t see it as a failure.

“There can be so much beauty in a love that doesn’t last forever,” he said. “And sometimes protecting the beauty of love means letting it go.”

So if you thought that “A Grey Area” might be a bitter breakup album, think again.

“Obviously, there’s a lot of different feelings that you go through over a year and a half post breakup, but this album, in many ways, is expressing how wholeheartedly I believe that love can be so meaningful without lasting forever,” said Saxe. “Having divorced parents makes it unavoidable to recognize that.”

While Saxe’s romance with Michaels may be over, his bromance with Mayer is still going strong. The two singer-songwriters bonded after “I had heard from a couple of friends that John had said some nice things about my songs,” he said. “So I reached out to him.”

Next thing he knew Mayer was playing guitar on “Here’s Hopin’,” a blues- and soul-streaked ballad from Saxe’s debut album, 2021’s “Dangerous Levels of Introspection.” And the “Daughters” singer is back on the axe grind for the new single “I Don’t Miss You,” a breezy pop ditty that he co-wrote for “A Grey Area.”

“To have someone you look up to and respect both as an artist and a person integrate themselves into your music — it’s an honor,” said Saxe. “And I really have a lot of love for that man.”

Having already opened for Mayer on tour earlier this spring — including a hometown concert at Scotiabank Arena in Toronto — Saxe has been learning well from the 45-year-old guitar god.

“He’s able to make an arena feel like you’re sitting beside him,” he said. “It feels like you’re just kicking it with him.”

Long before Mayer came along, though, Saxe got some early schooling from his late grandfather, János Starker, a Hungarian-born Holocaust survivor who went on to become a Grammy-winning cellist. And in addition to playing piano, guitar and bass on “A Grey Area,” Saxes honors his granddad by flexing his cello skills on the evocative, ethereal “Anywhere.”

“It’s about the people who are there for you even beyond their ability to be beside you,” he said, “and so playing the cello on that song was particularly sentimental.”

But despite his “built-in stage name,” Saxe does not count the saxophone among his instrumental credentials.

“I’ve been hearing that joke since I was f—king 5,” he said about his sax-y surname. “I love the saxophone, but I’m not sure it’s anywhere in my future.”