John Kander’s Major Chord, Undiminished

So it seems almost Sisyphean that while a music assistant is busy digitizing Kander’s archive and preparing the paper assets for eventual donation to the New York Public Library for the Performing Arts, the man himself is sitting nearby at a keyboard, cranking out more every day.

That’s not the right phrase, though. Even if he were in fact profoundly lazy, as Ebb insisted and Kander does not deny, composing is hardly drudgery for him. It’s more of a geological process, water rising from an aquifer, desperate to be tapped. If he doesn’t let the music out through his hands — or block it by listening to somebody else’s — it might drown him.

Which means he is always listening: Music plays in his head, he said, “like a radio you can’t turn off.” It began, he believes, some 35,000 John Kander Days ago, when, as a baby in Kansas City, Mo., he contracted tuberculosis. Isolated on a sleeping porch and able to sense his family only when they approached the screen door, he learned to associate the sound of footsteps coming toward him with the imminence of loved ones. “I think I began to organize sound in my head then, out of necessity.”

FOOTSTEPS GO BOTH WAYS though. If, as he said, a “residue of loneliness” remains from that experience, it’s a loneliness for which “the most fortunate antidote” has been companionship and collaboration. Though many people assumed that Kander and Ebb were a couple — their 45-year partnership was more intense and monogamous than many marriages — the men were not socially close. But he and Stephenson, a dancer in Kander and Ebb’s “The Act,” have been together since 1977, married since 2008. Some of Kander’s loveliest songs were written not for any show but for him.

As for collaboration, it’s no accident that Kander surrounds himself with a rotating roster of familiar names. “Next to the greatest sex you can imagine, making art with your friends is as good as it gets,” he said. He’s worked with Stroman six times, Thompson eight times and Washington, a featured performer in “The Scottsboro Boys,” twice. Half the music team are old Kander hands too, making the March 14 sitzprobe — the first rehearsal with the cast and the orchestra — a reunion and, as it happened, a party. You haven’t really heard “Happy Birthday” until a Broadway chorus of 37, accompanied by 19 crack musicians, sings it in a crowded, reverberant room.