“And I remember one morning, he came over with ‘I Want It That Way.’ That was probably my lucky day, because that song became so big.”

Swapping addresses, the two discovered that not only did they live in the same building, they’d unknowingly been living “door to door” while working together over previous months.“After that, he started knocking on my door to ask for lyrics or input on songs,” Carlsson says. The 99 Greatest Songs of 1999: Critics' Picks It was while Martin was working on tracks for the band’s hotly anticipated 1999 follow-up, Millennium, that Carlsson found himself helping out a neighbor in need, and subsequently being propelled to life-changing success. Martin, along with late Cheiron Studios founder and musical mastermind Denniz Pop, had worked with the Backstreet Boys on their first two records, Backstreet Boys and Backstreet’s Back - which were combined and released in the U.S. And it was all thanks to a shared cab ride home from work late one night with the man who would become one of his greatest collaborators - legendary writer/producer Max Martin.

While the Backstreet Boys may have influenced Carlsson’s swerve off stage to focus on writing music for others, they would also help cement his greatest songwriting coup, thanks to their success with a track he helped write one morning in Stockholm, Sweden: “I Want It That Way,” which turns 20 on Apr. “I got recruited to be part of the Cheiron family, who were at that show, then gave up my deal with BMG and my career as an artist.”

“All I understood after that was that I was a waste of time as an artist – because they were so good!” he reflects to Billboard.

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