After showcasing a panoply of virtually unknown performers in the 1960s — including Bob Dylan, Woody Allen, Lenny Bruce, Bill Cosby, Randy Newman, Nina Simone, and Peter, Paul and Mary — Mr. Weintraub became a Hollywood producer.

He introduced Bruce Lee and the martial arts craze to US movie audiences and persuaded Warner Bros. to subsidize the last-minute cost of a three-day rock festival near Bethel, N.Y., in 1969. The investment resulted in the studio’s Oscar-winning documentary “Woodstock.”

The Bitter End’s signature stage backdrop — a bare 150-year-old brick wall — helped distinguish it from other popular bohemian hangouts like the Village Gate and the Village Vanguard. It appeared on the cover of Peter, Paul and Mary’s first album.

A radio show hosted by the folk singer Theodore Bikel originated there. So did a later television series, “Live at the Bitter End.” In the 1963-1964 season, Mr. Weintraub was the talent coordinator for “Hootenanny,” a weekly folk music show on ABC-TV.

“This was the beginning of the social revolution that ended up being called the ’60s,” Harold Leventhal, a musicians’ manager, wrote in a reminiscence on Mr. Weintraub’s website.

“It wasn’t actually born there at the Bitter End; it was really born with the Weavers and in the protest movements and folk singers of much earlier times,” Leventhal continued. “But what’s important, and what’s so special about Freddie, is that it all surfaced at the Bitter End. It was nurtured there.”

The bearded, 6-foot-2 rebel who nurtured the neophytes was an improbable muse.

Fred Robert Weintraub was born in 1928, in the Bronx, N.Y., to Meier Weintraub, who owned a toy and baby-carriage business, and the former Anna Bogatz.

He studied for his bar mitzvah with the cantor Reuben Tucker, who later, as Richard Tucker, sang at the Metropolitan Opera. He attended William Howard Taft High School and graduated from the Fieldston School, both in the Bronx, and later the Wharton School of the University of Pennsylvania.

In addition to his fourth wife, the former Jackie Dubey, a film producer, he leaves four children from his earlier marriages — Sandra, Barbara, Max, and Zachary Weintraub — and four grandchildren.

Mr. Weintraub said he had expanded his father’s business, Darling Furniture and Toys, to dozens of stores and was living with his wife and daughters in Westchester County, N.Y., when, at 26, he was struck by the Fellini film “La Strada.” He immediately identified with the film’s itinerant strong man, Zampano, played by Anthony Quinn, whom he recalled “clawing at the sand in despair.”

He soon left his wife and daughters (this was the second time he left home; he had also run away at 12) for a freewheeling life, playing the piano in a bordello, operating a fishing boat in Cuba, and roaming Europe before deciding that the Greenwich Village music scene was where he belonged.

He opened the Bitter End, at 147 Bleecker St., in 1961. According to various accounts, the name was either suggested by its nocturnal appearance or recommended by his mentor, Tom Murray, who, for some reason, drew his inspiration from the nautical term for the rags that mark the last few feet of an anchor rope.

The club had no liquor license, but served coffee-and-ice-cream confections with names like Frosty Freud and Zen Sundae. It fancied itself so far out, according to the menu, that a customer who ordered espresso was considered square. Mr. Weintraub’s office was typically al fresco: out front, for example, his foot perched on a bumper of a parked car.

In 1965, Mr. Weintraub hired Paul Colby to manage the club. Mr. Weintraub fired Colby after Colby opened a bar next door called the Other End, and then Mr. Weintraub sold the Bitter End to Colby in 1974. (Colby acquired the rights to the name a decade later. He died in 2014.)

Over the years, the Bitter End provided a stage to a parade of budding singers, including Harry Chapin, Neil Diamond, Bette Midler, and Carly Simon, and young comedians, among them Dick Cavett, George Carlin, Billy Crystal, Robert Klein, Joan Rivers, Lily Tomlin, and Flip Wilson.

“Woodstock” was Weintraub’s first project after joining Warner Bros., where he later became a vice president for creative services. The critic Roger Ebert called it “the film that gave a generation a voice and made Woodstock a part of American myth.”

When the Woodstock festival began in chaos, with miles-long traffic jams and rain-soaked fields, Mr. Weintraub was a laughingstock at Warner Bros. But by the time the weekend had ended and Woodstock had made history, he was lionized. The documentary became the sixth-highest-grossing film of 1970.

“By Monday morning I was a bigger hero than Neil Armstrong,” Mr. Weintraub recalled in his autobiography, “Bruce Lee, Woodstock and Me: From the Man Behind a Half-Century of Music, Movies and Martial Arts” (2011, written with David Fields). “All he did was walk on the moon. I saved Warner Bros.” (The moon landing had occurred less than a month before the festival.)

The first film he produced through his own company was the Bruce Lee martial-arts hit “Enter the Dragon.” He produced or wrote about 50 more films. Most recently, he was developing a TV series about the Bitter End.

Mr. Weintraub was supposed to play himself in the 1993 film “Dragon: The Bruce Lee Story,” but at the Hollywood premiere he was informed that his footage had been cut from the final version.

“You weren’t believable as Fred Weintraub,” he recalled the director, Rob Cohen, telling him.

Mr. Weintraub explained, on his website, “In my defense, I’ve never pretended to be an actor, and ‘Fred Weintraub’ is a mighty difficult role.”

“He’s passionate, unpredictable, lusty, mischievous, impatient, and larger than life,” Mr. Weintraub said of himself. “And his back story places him at the heart of more pop culture milestones than seems possible for any one man.

“He’s like Forrest Gump as played by Al Pacino,” he added. “I’ve acted the part my entire life, and I’m still amazed that a child born with incurable shpilkes (the clinical term for ‘ants in my pants’) could accomplish so much.”