SANTA MONICA, CA.- When he was 16, Jack Browne sat down at his parents’ kitchen table in Fullerton, California, and started picking out a tune on an old Kay guitar.

In 1965, the fledgling songwriter and high school junior — inspired by books, records and his own suburban disaffection — began weaving together an existential number about loss and regret called “These Days.”

It would be a year until he finished the song, nearly a decade before he recorded it properly. By the time Jackson Browne, as he would be known professionally, cut it for his 1973 album “For Everyman” — which will be reissued Sept. 20 — it had already been done in two distinct, definitive versions: the first by German chanteuse and Velvet Underground collaborator Nico, then later by Southern rocker Gregg Allman.

“These Days” has proved a remarkably durable composition, reinterpreted by Cher, St. Vincent, Glen Campbell, Miley Cyrus, Paul Westerberg and Drake, to name a handful. It inspired Wes Anderson’s 2001 film “The Royal Tenenbaums,” and more recently has become the unlikely soundtrack to a series of TikTok trends.

While Browne has had bigger hits as an artist (“Doctor My Eyes,” “Running on Empty”) and as a writer (Eagles’ “Take It Easy”), “These Days” has rambled through the decades, morphing musically, changing lyrically and taking on added layers of meaning. “In that regard, it’s sort of like a folk song,” Browne said on a late August afternoon, sitting in the control room of his Santa Monica recording studio, Groove Masters.

“I come from folk music, that was my school,” continued Browne, somehow still boyish and bright-eyed at 75. “You’d learn several versions of the same song and adapt the parts of it that you liked and it’d become something else. That’s what’s happened with ‘These Days.’”

Part of the enduring power of “These Days” is its paradox: Written by a teenager at the start of his path, it’s often been delivered as a lament by someone looking back on their life — the denouement coming in its final lines: “Please don’t confront me with my failures/I had not forgotten them.”

“That song was so much further along life’s journey than Jackson had been at that point,” Bonnie Raitt, a friend, said in an interview. “That he was so wise at 16 is unbelievable to me. It’s a song that’s reflective of so many eras of life. He’s saying things that spoke to me then, as a young woman, and they speak to me now. I think that’s why so many people relate to it.”

Historically, Browne has been reluctant to look back on his career and seems almost puzzled that the origins of “These Days” should be of any particular interest. “When you’re writing a song,” he said, “you’re more concerned about the actual nuts and bolts of how to make a melody go with a chord progression. You don’t ever stand back and think: ‘I’m carving something that people will be singing 60 years from now.’”

Though he was born in Heidelberg, Germany, where his father worked for The Stars and Stripes military newspaper, the Brownes were deeply rooted Angelenos, and he spent his childhood in Highland Park. The family’s move to Orange County in the early ’60s, where Browne attended Sunny Hills High School, might have put him in a more a conservative environment, but Browne soon found a music scene centered on the Paradox, a club where he would watch rising folk stars like Tim Buckley and seasoned blues veterans like Sonny Terry and Brownie McGhee play up close. With the arrival of the Beatles and the radical evolution of Bob Dylan, an inspired Browne soon went from learning other people’s songs to writing his own.

He found further sustenance in the era’s literary works. “I remember opening James Baldwin’s ‘The Fire Next Time,’” Browne said of the 1963 essay collection on race, “reading one page, closing it and starting to play the guitar and writing a song. It was the language that excited me, and the emotion.” He said “These Days” was influenced by Jack Kerouac’s “On the Road” and a series of volumes on the troubled life of Vincent van Gogh, particularly Irving Stone’s “Lust for Life.”

Jimmie Fadden, a co-founder of the Nitty Gritty Dirt Band — which Browne briefly joined — recalled the young Browne as both preternaturally gifted and devoted to his craft.

“I walked out back of the Paradox to smoke one night,” Fadden said, “and I saw Jack sitting on a parking curb, writing. He was messing with ‘These Days.’ I don’t know what his failures were at that time — maybe it was his report card, or school credits or the authorities at Sunny Hills coming down hard on him. All these years later, it’s a perfect song for any of us in our 70s.”

Although he acknowledges “These Days” has often been presented as a valedictory, Browne still hears it as a “young song.”

“Teenagers have a very vibrant emotional life,” he said. “There’s so much going on in terms of your ideas about personal freedom and what the world is supposed to hold for you.” Even the song’s deep sense of resignation — captured in lines like “I stopped my dreaming” — felt authentic. “Some young people do give up really early,” Browne said. “They get conscripted into a certain kind of life; they’re told this is how to succeed, or this is how people will like you, or this is what you can do to be a success. And that was one of the things that we all really rebelled against.”

A few months after his 1966 high school graduation, Browne headed to New York City, having landed a deal with Elektra Records’ publishing division, Nina Music. In January ’67, he made the first demo recording of “These Days” at the home of producer Peter K. Siegel. On that version of the song, Browne had yet to find his ultimate singing voice and delivered it an unusually expansive style. “That was very influenced by Tim Buckley, I think, without knowing it,” he said.

It was Buckley who got Browne a job in New York: a gig accompanying Nico on guitar, as she performed a residency at the St. Marks Place nightclub the Dom. (Their musical collaboration led to a brief romance.)

At the time, Nico was starting her solo career, putting together material for what would become her debut LP, “Chelsea Girl.” “I hate to shatter any illusions of Nico as this disaffected goddess,” Browne said, “but what she was doing was similar to what Judy Collins was doing at the time, and what Linda Ronstadt and Bonnie Raitt would later do — collecting great songs that nobody else had done.”

In addition to songs by Dylan and Lou Reed, Nico recorded a trio of Browne compositions for the album in April ’67. Her manager, Andy Warhol, wanted Browne to lose the acoustic guitar on “These Days.” He “was contemptuous of folk music, he wanted her more modern sounding,” Browne recalled.

Browne borrowed an electric from a friend, used a capo to adjust for Nico’s low singing voice, and switched from flatpicking to finger picking, resulting in the song’s ethereal chiming quality. Producer Tom Wilson further fleshed out the track, hiring composer Larry Fallon to create a melancholy string backing — an embellishment that Nico hated. But between her unconventional phrasing and the evocative arrangement, it yielded a kind of strange magic.

“It took the crucible of the recording studio for me to realize what it was,” Browne said. “She found a way of expressing the words in a truthful way. It’s very sad to hear someone say they’re going to give up dreaming, to hear a young woman say that. It really moved me. That’s when I thought, ‘This might be a good song.’”

IN 1968, BROWNE’S pals in the Nitty Gritty Dirt Band offered up a jaunty, horn-fueled version. Nashville artist Johnny Darrell released it as a country single two years later. Producer (and onetime Manson Family target) Terry Melcher fashioned a beguiling chamber pop version for his solo album, done as a duet with his mother, Doris Day.

Then, in 1973, Browne’s friend Allman recorded it for his first solo album, “Laid Back.” Allman’s elegiac reading, coming after the recent deaths of his brother Duane and bandmate Berry Oakley, reshaped the song.

“He changed it in wonderful ways,” Browne said, noting that Allman took out the “annoying” major 7th chord, slowed its tempo and tweaked the final lyrics. “It was beautifully understated,” he added, “because everything about him was.”

After the success of Browne’s 1972 self-titled debut, he finally returned to “These Days,” recording it for his sophomore LP, “For Everyman.” “My version was very influenced by Gregg’s,” said Browne, who also changed the line “I’ve stopped my dreaming” to the more hopeful “I’ll keep on moving.” “That was a good reason to go back to it,” he said. “‘I’ll keep on moving’ is the way of all my songs — no matter how morose they might be, I try to leave saying something uplifting.”

As his career went on, “These Days” would float in and out of Browne’s live sets. “I didn’t do it for many years, I just lost track of it,” he said. “But then other people would cover it. They would learn the song and then I’d learn it back.”

In the ’80s and ’90s, a slew of alternative acts (10,000 Maniacs, Everything but the Girl, Elliott Smith, Mary Lou Lord) recorded or performed “These Days,” drawing heavily on Nico’s recording — which took on an added resonance following her 1988 death at 49. “Nico’s version became a touchstone,” Browne said. “It’s not only the sound of it, and who she was when she was younger, but also what became of her. It got enveloped into her story.”

It was Nico’s rendition that caught the ear of Wes Anderson after his friend, actress and singer China Forbes, turned him on to “Chelsea Girl” in the early ’90s. “She played the song for me the first time,” Anderson wrote in an email, “and somehow it inspired a whole movie, really and truly.”

His “Royal Tenenbaums” used “These Days” in a slow-motion introduction of Gwyneth Paltrow’s character, Margot Tenenbaum — a flashpoint moment from which Anderson developed the whole idea for the picture. “There has never been anything sweetly sadder or more evocative,” Anderson said of the song.

Browne had approved Anderson’s use of “These Days,” but had forgotten about it completely by the time he bought a ticket to see it at his local theater. “When the scene started and the song came on, I thought, ‘Wow, I used to play just like that,’” Browne said, laughing. “Then I realized it was me. I think the song had already taken on a life of its own, but it was definitely amplified by that movie.”

Asked for his favorite version, Browne pulled out his phone and played a recording by his friend, Cuban musician Carlos Varela. A mostly Spanish-language interpretation, Varela’s is a meditation on his difficult relationship to his homeland (“Havana was my lover, but things can never be the same”). “Which is a sign of a good song, other than just being enduring,” Browne said, “that it can be adapted to this totally other realm.”

Browne released reworked live versions of “These Days” on his 2005 “Acoustic Vol. 1” album and the 2017 collection “The Road East,” and continues to perform it in concert. What goes through the mind of 75-year-old man singing the words he wrote as a 16-year-old boy?

“Well, I’m not thinking about the same thing I did when I wrote it,” Browne said. “Mainly, I’m thinking about life now. If a song is worth anything, it’s about the life of the listener. And I become a listener, too, when I sing it.”

This article originally appeared in The New York Times.