Paul Simon had only one request of the filmmaker undertaking “In Restless Dreams,” a documentary about his life: “He wanted the music to sound good,” director-producer Alex Gibney said.

Over the years, Gibney, 70, has told the stories of many lives, including Elizabeth Holmes’ (“The Inventor: Out for Blood in Silicon Valley”), Lance Armstrong’s (“The Armstrong Lie”) and Dilawar’s, an Afghan farmer who was tortured to death by U.S. soldiers in 2002 (“Taxi to the Dark Side,” for which he won an Academy Award for best documentary feature). He’s taken on musical legends like James Brown, Janis Joplin and Frank Sinatra.

The Simon film, however, came with the most tempting of offers: a chance to come out to the singer’s ranch in Wimberley, Texas, and film him as he worked on his latest album, “Seven Psalms,” which was released last year.

“That sort of thing doesn’t happen often at all,” Gibney said. “I got myself down to Texas as quickly as possible.”

“In Restless Dreams,” which premiered Sunday on MGM+ (for TV viewers, the film is split in two, with the second half airing March 24), begins with Simon’s earliest days growing up in Queens, New York, as he and his onetime musical partner Art Garfunkel learned to harmonize by listening to the Everly Brothers. We see Simon (and sometimes Garfunkel) create beloved albums including “Sounds of Silence,” “Bridge Over Troubled Water” and “Graceland”; perform in Central Park in 1981, a concert that attracted half a million fans and led to a brief reunion of the duo; and tackle everything from movie soundtracks (“The Graduate”) to acting roles (“One-Trick Pony”).

There are several scenes of Simon working on some of American pop music’s most memorable tunes in a manner that has long impressed contemporaries like Wynton Marsalis, who met Simon in 2002. “He has a mystical understanding,” Marsalis said in a video interview. “He can see the timeless through the specific.”

“He was like that when he was a kid,” Marsalis continued. “If you know the age he was when he wrote ‘The Sound of Silence,’ that’s all you need to know.” (Simon was 21).

Filming for “In Restless Dreams” began in the summer of 2021, after Simon and Gibney came to a mutual agreement about the movie. “We both decided that it would be my film and my interpretation,” Gibney said. “Paul has a reputation as being a somewhat prickly character, so I didn’t know exactly what I was going to get,” he added. “So I was surprised, frankly, that over time, he was willing to share quite a lot, including his trials and tribulations with his health.”

When Gibney arrived at Wimberley, Simon, 82, was losing his hearing in his left ear, which affected his ability to hear pitches and sing in tune. Expecting to memorialize a master songwriter at work on what would become a particularly personal album — Jon Pareles of The New York Times called it “observant, elliptical, perpetually questioning and quietly encompassing” — he captured something that was, in many ways, all the more poignant because of the struggle behind its creation.

“You saw a guy who was used to being extremely healthy and athletic for most of his life, and now, suddenly, things were happening that he couldn’t control,” Gibney said.

Marsalis, who makes several appearances in the film, admitted it was a hard thing to watch. “But he doesn’t whine, you know. He’s not like ‘woe is me.’ He’s just trying to find solutions to problems.”

At one point in the film, Marsalis launches into an extended list of things that he and Simon have talked about over the years, from the personal (being divorced, having children, “being at your father’s rehearsal that you don’t want to be at”) to the political (race relations in the United States, the direction the country is going in) to the artistic (Bach vs. Beethoven, Duke Ellington’s musical output in 1962, “what does it take to write a song”). The list, delivered at a speedy clip, goes on for nearly a minute.

“That’s one of these great moments that happen that you could never expect,” said Andy Grieve, the film’s editor. “It just quickly paints such a vivid picture of that friendship.”

Gibney said he found the moment remarkable: “I don’t know if could remember a list that long,” he said. “It was a reckoning.”

At another point, Grieve pairs contemporary audio of Simon speaking about the dissolution of his friendship with Garfunkel with archival footage of the two young men, at the height of their fame, sweetly singing and scatting to “The 59th Street Bridge Song (Feelin’ Groovy)” on a hotel bed.

“That was a lovely moment that Andy intuited and put together,” Gibney said. “The contrast between that love and then the bitterness laid over that sweet moment captured in a poetic way the ebb and flow of time and memory, happiness and sadness, all rolled into one.”

According to Simon, the inspiration for “Seven Psalms” came to him in a dream in 2019. Gibney filmed him as he rehearsed and recorded the album in Wimberley, Austin, Houston and New York, directed singers and instrumentalists, and sang alongside his wife, musician Edie Brickell.

The filmmakers also pored through hundreds of hours of audiotapes and archival footage and thousands of photos, many from Simon’s own collection. Simon lived much of his life in front of the camera, so it was less a matter of finding, say, footage of him singing “Cecilia,” than it was of choosing which version out of dozens of them was the best.

The movie offers a wealth of interesting trivia, such as how actor Charles Grodin directed the documentary “Simon and Garfunkel: Songs of America” in 1969, and then appeared as a Garfunkel impersonator, complete with a wig, alongside Simon in a “Saturday Night Live” skit. Or how the organizers of the 1967 Monterey Pop Festival expected Simon and Garfunkel, as well as fellow acts Jimi Hendrix and Janis Joplin, to “perform without fee.”

As for the songs, there are many, and many of them played at length (the entirety of “American Tune”; Aretha Franklin’s powerful 1971 cover of “Bridge Over Troubled Water”). Simon’s discography is so extensive and hit-filled that “Kodachrome” — “Kodachrome”! — doesn’t even make an appearance. “It’s already a three-and-half-hour movie,” Grieve said. “If we put in every amazing song, you’d have a 10-part series.”

For Gibney, who has made many films over the years about villains and cheats, corruption and deception, being able to tell the story of such a beloved songwriter was a welcome change. “I love his music, so this was a labor of love in the truest sense,” he said.

Not that it was an easy story to tell. “It’s a story of struggle,” he said. “But without the struggle, it would have been a less interesting film. It would have been a greatest hits film. But the struggle of trying to reckon with your own mortality, even as you’re creating, and how that relates to the entirety of your life? That’s potent.”

The New York Times News Service