But they both began as little boys who loved to sing.

Mr. Paul, a talented pianist, started early. At age 3, he was singing gospel music with his father, a pastor, in church. Later, he sang and danced at senior centers with Music Theater of Connecticut; and then, at Staples High School, he performed in “Into the Woods,” conducted the orchestra in “Hello, Dolly!” and spent his free time poring over Broadway “fake books,” which help pianists master melodies.

Mr. Pasek also sang with a parent: His mother is a developmental psychologist and professor with a propensity for bursting into song. (“She’s like a real-life musical theater character, in the best possible way,” he said.) She wrote and performed songs from a child’s point of view (“They were a big hit on the synagogue circuit,” he said), and he remembers guest starring with her at about age 7.

Mr. Pasek sang and traveled with the Philadelphia Boys Choir & Chorale, and then, as a student at Friends Central School, performed in musicals including “Bye Bye Birdie” and “42nd Street.”

They compare themselves to brothers, who bicker and bond, knowing their relationship will endure. A recent fight, over whose bad habits were to blame for their difficulty replacing the final first act song in “Dear Evan Hansen,” sent Mr. Pasek stalking out of their Columbus Circle studio into the street, but then, 10 minutes later, calling Mr. Paul for a lengthy air-clearing that prompted the pair to ditch the disputed number and start over.

Mr. Pasek and Mr. Paul met the summer before college, at a freshman orientation weekend, and connected over a shared sense of humor, a passion for the work of Jason Robert Brown and an obsession with “Merrily We Roll Along.” (The title “Edges” alludes to a “Merrily” lyric.) Mr. Pasek wanted to record some songs he had written as a high school senior, and he recruited Mr. Paul as an arranger and accompanist; with that, their collaboration began.

They mined their own experiences, and those of their friends, for material, acting out songs as they wrote. “I kept watching them observe the social experiment of college and find ways to articulate it,” said Nick Blaemire, a fellow Michigan student who is now an actor in New York, recalling a night when he told Mr. Pasek about his difficulty expressing love to a girlfriend, and seeing that become “I Hmm You.”