“All we could hear, any of us, were the bad parts,” recalled Tom Jones, who wrote the book and lyrics for the show. The rest of the night, he said, was spent drinking in Central Park and wondering if the show was doomed.

Instead, “The Fantasticks” managed to keep going. And going. It ran for an astonishing 42 years and earned a place in theater history for its co-creators, composer Harvey Schmidt and Mr. Jones, who died Friday at his home in Sharon, Conn., at 95.

“The Fantasticks” stayed at the 150-seat Sullivan Street Playhouse until 2002 — more than 17,160 performances, as the longest-running musical in American theater history — and reached audiences around the world with adaptations from Tokyo to Tehran and beyond. The play’s melancholy opening song, “Try to Remember,” introduced onstage by Jerry Orbach, was recorded by stars such as Perry Como, Harry Belafonte, Barbra Streisand and Plácido Domingo and whose lyrics by Mr. Jones became part of the American songbook.

Try to remember the kind of September

When life was slow and oh, so mellow.

Try to remember the kind of September

When grass was green and grain was yellow.

“The Fantasticks” was revived in 2006 at the Snapple Theater Center, later renamed the Theater Center, in Times Square. It closed in 2017, surpassing 21,550 performances and, along the way, reflecting the passing decades.

The show in the early 1960s had cast members in bobby socks and penny loafers and, two generations later, the love-struck kids were steeped in smartphones. (In London, the Agatha Christie whodunit “The Mousetrap” has been performed nearly 29,000 times since 1952 but moved among various theaters.)

“My mind doesn’t grasp it, in a way,” Mr. Jones told the Associated Press in 2013 about “The Fantasticks” run. “It’s like life itself — you get used to it and you don’t notice how extraordinary it is.”

Mr. Jones and Schmidt, who died in 2018, never managed to reprise such unalloyed success with their Broadway musicals. The work “110 in the Shade” opened in 1963 and ran for 330 performances (with book by N. Richard Nash); “I Do! I Do!” had a run of more than 500 shows from 1966 to 1968. Both shows, however, earned Tony Award nominations, and a version of “My Cup Runneth Over,” a song from “I Do! I Do!,” cracked the Top 10 on the Billboard Hot 100 chart in 1967.

The singular success of “The Fantasticks” still leaves drama students, critics and theater mavens trying to explain its magic. Mr. Jones often attributed the show’s longevity to its simplicity. The story is the stuff of fables: A boy, a girl and two fathers who concoct a feud to try to bring them together.

The show’s creative partnership began in Texas. Mr. Jones and Schmidt collaborated on songs and plays as students at the University of Texas. After graduation, Mr. Jones and another composer, John Donald Robb, staged a play in 1956 at the University of New Mexico, “Joy Comes to Dead Horse,” that was loosely based on Edmond Rostand’s late-19th-century comedy “Les Romanesques,” about fathers plotting to get their children into a romance.

Mr. Jones then reunited with Schmidt in attempts to bring an iteration of “Dead Horse” to Broadway. A director, Charles “Word” Baker, offered a chance to present a scaled-down version at New York’s Barnard College. Mr. Jones and Schmidt rebuilt their play leaner and virtually without set design. (Some troupes have used a broom to suggest the wall.)

Mr. Jones said they borrowed some elements of historical theater, including the mostly bare stage of Elizabethan theater that relies on audience imagination.

“Since we were no longer aiming for Broadway, we decided to go ahead and attempt all the things we had been dreaming of doing for years,” Mr. Jones said. “After all, we had nothing to lose.”

They tweaked the plot to have the fathers arrange a fake abduction of the girl, Luisa, so that the boy, Matt, can make a heroic rescue. “The fathers refer to Luisa and Matt as being ‘fantastic,’” Mr. Jones told New York Lifestyles Magazine in 2018. “I added the ‘k’ to make it sound more mysterious.”

In the audience at Barnard was theater producer Lore Noto, who took the show to the Sullivan Street Playhouse. The producers spent $900 on the set and about $540 on costumes, at a time when a major Broadway show could cost $250,000 to launch.

The low-cost investment may have been a saving grace. Mr. Jones said some of the performances after opening night were for audiences of as few as 10 people. He recalled that sometimes the cast could hear a snoring theatergoer.

“It was amazing that we had a second night, much less that we were able to run that first week with hardly any audience,” he said. “What had we done wrong? What had we done right?”

T. Collins Jones, Esquire

Thomas Collins Jones was born in Littlefield, Tex., on Feb. 17, 1928, and raised near the middle of the state in Coleman. His father was a turkey farmer, and his mother was a homemaker.

Mr. Jones said that he intentionally stood out in rural Texas. As a high school sophomore, he became what he called a “character,” wearing a bow tie and straw hat and smoking a pipe. He adopted the byline “T. Collins Jones, Esquire” for articles in the school newspaper.

Then, at the University of Texas drama department, he discovered “there were other people actually like me,” he said. “Here, marvel of marvels, everybody was T. Collins Jones, Esquire.” He graduated in 1949 and stayed at the university to earn a master’s degree in theater in 1951. He later served in a counterintelligence unit during the Korean War.

On the opening night of “The Fantasticks,” Mr. Jones appeared in the role of “the actor,” who is hired by the two fathers to stage an abduction to end the fake feud. He used the name Thomas Brice on the playbill because he didn’t want the show to be perceived as a “vanity” project. In 2010, to mark the show’s 50th anniversary, he again joined the cast.

Mr. Jones was inducted into the American Theater Hall of Fame in 1998. He took special pride in “Try to Remember,” saying he sought to create a moment in time to “see it with your ears.”

“That special place where once — just once in your crowded, sunlit lifetime — you hid away in shadows from the tyranny of time,” he said.

Mr. Jones’s marriage to Eleanor Wright ended in divorce. His second wife, choreographer Janet Watson, died in 2016. Survivors include two sons from his second marriage. Mr. Jones had cancer, said Dan Shaheen, a co-producer of “The Fantasticks.”

Outside the theater world, Mr. Jones said he was often mistaken — on paper at least — for his namesake, the Welsh singer of hits such as “What’s New Pussycat?” Once on a plane, the flight attendants assumed the Tom Jones on the passenger manifest was the singer, he told the Boston Globe in 1990. They were crestfallen.

“He’s not the real Tom Jones,” Mr. Jones laughed, recounting one of the flight attendants as saying.