Spielberg, who was visibly taken aback at Williams’ change of plans, cracked, “I’d better get to work to find out what the hell I’m doing next!”

Between carefully curated clips from some of the 29 films they have teamed up for, Spielberg and Williams discussed how they met (a Universal exec suggested that Spielberg, a young director, and Williams, an up-and-coming composer, meet for lunch), how they work together. Williams rarely accepts Spielberg’s offer to read a script prior to production, opting instead to wait until it’s done, at which points, Spielberg says, “John sees the movie, then we sit down the next day, and we just start discussing where there should or should not be music” and they spoke about the role that music plays in the movies, generally, and in their movies, specifically.

“Music is probably older than language,” Williams asserted. “It is a very important thing in all of us — when we’re grieving, when we’re happy. We don’t know why. It’s unknowable.”

As for how he determines if a film scene does or does not require musical accompaniment? “In the end, the film tells us, if we pay attention enough. It’s mainly intuitive.” Spielberg paid tribute Williams’ contributions by stating, “I tell a story, and then John retells the story musically.”

When they first sat down together, Spielberg “seemed to know more about film music than I did,” Williams realized, so Williams agreed to work with him on Sugarland Express. They began on that film in 1972, it was released in 1974, and then a year later came Jaws, the first of their truly immortal collaborations. Of Williams’ simple but haunting score for that thriller, Spielberg admitted to Williams, “I was scared when you first played it for me on the piano. I didn’t know you that well. I thought you were pulling my leg.” But Williams had hit on something: “You could play it very softly or very quickly, or soft or loud, so you could kind of manipulate an audience,” he explained.

Music was a central part of the plot of 1977’s Close Encounters of the Third Kind, with its five-note signature tune — arrived at after 100 permutations were considered — representing a means of communication between humans and aliens. The only “bad music” in the film was deliberately included, and was played by Spielberg himself when Williams asked him to step in for clarinetist whose playing was too polished for what a scene required.

Discussing 1981’s Raiders of the Lost Ark and 1982’s E.T., with their iconic themes, Williams said to Spielberg, “You and I have always been talking about tempo on films,” observing that the addition of music can make four minutes of screen time feel like two.

Sometimes, the duo explained, less is actually more when it comes to music in films. They said they never even considered incorporating music into the famous opening sequence of 1998’s Saving Private Ryan, but decided to employ the trumpet and low strings to stir emotion in later scenes, most famously in the hushed and reverential choral finale. “Musically, it honors all of the veterans, both today and yesterday,” Spielberg said of Williams’ composition for that film, “and it’s why the military is always asking if they can play this score.”

The recording of Williams’ score for 2012’s Lincoln, which was inspired by 19^th century American music, with trumpets at the fore, moved Spielberg and Williams to tears.

But for Spielberg, who lost both of his parents in recent years, and for Williams, who had known both of them, The Fabelmans was a special undertaking.

“For me,” Spielberg professed, “it was the most private and personal experience of my whole career.” Speaking on what would have been Spielberg’s mother’s 103rd birthday, Williams said of his score — which has already been nominated for Golden Globe and Critics Choice — “I hope it is worthy of them,” to which Spielberg quickly responded, “Oh, it is.”

Asked to sum up their half-century of making movie magic together, Williams said of Spielberg, “I’ve enjoyed his company and the pleasure and the gift of his inspiration. Can a muse be a man? He’s certainly been a muse for me.”

Spielberg said that working with Williams had been like ideal marriage. “I don’t think we’ve ever had a disagreement,” he volunteered, before adding with a chuckle, “I mean, what am I going to do? Sit down and write the music myself?”

“In the art form that we’ve both chosen, he has been the most steadfast brother and collaborator that I’ve ever had in my life. And that’s how I would sum up how much I love you.”