'American Masters' profiles songwriter Marvin Hamlisch

He was a singular composer but, like everyone, his career was marked by highs and lows.

Now Marvin Hamlisch, who changed Broadway and won a Tony and a Pulitzer for “A Chorus Line,” is the subject of the “American Masters” bio “What He Did for Love.”

“I worked with Marvin and wanted to celebrate his life,” says Dori Berinstein, who wrote and directed the documentary, airing Friday at 9 p.m. on PBS. “Marvin was at his happiest collaborating.”

Berinstein, the brains behind “Carol Channing: Larger Than Life” and “ShowBusiness: The Road to Broadway,” began doing interviews and archival research for this project in October 2012, two months after Hamlisch’s death.

“The conceit is that I wanted Marvin to tell his story,” she says. “We dug deep to find footage that’s not been seen before.” Family home movies were a prime source. One shows a pint-size Hamlisch, who was declared a prodigy at age 4, tickling the ivories two years later as a student at Juilliard.

About half the doc comes from Berinstein’s one-on-ones with Hamlisch’s circle: his widow, Terre Blair Hamlisch, high-school pals Christopher Walken and Leslie Uggams, and Yankee manager Joe Torre, who sings a snippet from “A Chorus Line.”

Barbra Streisand recalls meeting Hamlisch when he was a rehearsal pianist on “Funny Girl.” They bonded over music — and chocolate doughnuts. They later bonded over Academy Awards for “The Way We Were.”

Carly Simon met Hamlisch when she sang “Nobody Does It Better,” the theme to “The Spy Who Loved Me.” Hamlisch wrote the sexy 007 anthem with Carole Bayer Sager.

“The first time I met Marvin, I mistook him for a tax collector,” Simon says. “I just had never met anyone who looked like Marvin who was in the music business. It was a dish of a song.”

The same goes for Hamlisch, says Berinstein. “He had a giant heart.”