New York ? Luther Henderson speaks humbly of the experience that sparked his interest in musical theater. It happened nearly 70 years ago, when the orchestrator and pianist was a teen-ager growing up in Harlem.

It was something he would never forget: He saw the original production of George and Ira Gershwin’s “Porgy and Bess.”

The music, he says simply, “just bowled me over.”

That was in 1935, the same year Langston Hughes wrote the comedy “Little Ham.” In September, a musical version of the play, enlivened by Henderson’s authentic orchestrations and 50-plus years of theater experience, opened at off-Broadway’s John Houseman Theater.

And Henderson is still at work. At 83, he is looking ahead to his next project, which involves some business left unfinished a half century ago.

“Oh, the delights of old age,” Henderson says coyly, pausing for a sip of water to clear his throat.

Sitting in his Manhattan apartment, he reflects on a career that has spanned more than two dozen Broadway shows and several generations of performers. His long list of credits includes the original production of the Fats Waller musical revue “Ain’t Misbehavin”‘ (1978), and Tony Award nominations for his work on “Jelly’s Last Jam” (1992) and “Play On” (1997).

Henderson took a varied path to the very specific craft of orchestrating and arranging musicals, one that led him through jazz and classical symphonic music. And at one time, there were even early aspirations of becoming a mathematician. “Unfortunately, I got 100 percent on one of those geometry regents,” he says.

Henderson’s family moved to New York from Kansas City, Mo., when he was 4. They settled in the Sugar Hill section of Harlem, where they became close neighbors of Duke Ellington’s family. Henderson’s longtime friendship with Ellington’s son, Mercer, began at an early age.

In “Little Ham,” the show’s hero, Hamlet Hitchcock Jones or “Ham” is a flighty philanderer who resolves to save Harlem from the grips of money-extorting white gangsters. His devotion to the place Hughes also called home is manifest in the soft ballad “Harlem, You’re My Girl.”

The intimate attachment to 1930s Harlem, a period of intense artistic creativity, is something Henderson shares with both Ham and Hughes, a poet, novelist, playwright, short story writer who was a compelling presence during the Harlem Renaissance. And the familiar backdrop, both geographic and figurative, gives the show special meaning to the orchestrator.

The show is, he says, about hope.

“It’s no accident that so many musical and artistic geniuses came from underprivileged people. They haven’t a choice but to dream.”

Henderson grew up listening to “a little bit of everything” from Ellington and Waller to classical music. After college, he was classically trained at New York’s Juilliard School. He also studied music at New York University.

“At that time, if you got caught practicing jazz, you would be expelled.”

That didn’t stop him and his classmates from having the occasional jam session in a practice room, but one student would always stand lookout. If the dean was spotted walking down the hall, “it was back to Bach and Beethoven.”

Henderson is quick to point out it was his parents who instilled in him his academic drive. His father was a college education professor, his mother an elementary school teacher.

During his four and a half years at Juilliard, he played trio gigs around Manhattan in his free time. After graduating, Ellington called on him to arrange some of his compositions for a performance by a classical symphony orchestra.