My favorite film of 1977 was not “Star Wars” but “Close Encounters of the Third Kind,” Steven Spielberg’s U.F.O fantasia. Notwithstanding the fact that I was nine years old, I considered “Star Wars” a little childish. Also, the trash-compactor scene scared me. “Close Encounters,” on the other hand, drew me back to the theatre—the late, great K-B Cinema, in Washington, D.C.—five or six times. I irritated friends by insisting that it was better than “Star Wars,” and followed the box-office grosses in the forlorn hope that my favorite would surpass its rival.

“Close Encounters” still strikes me as an amazing creation—a one-off fusion of blockbuster spectacle with the disheveled realism of nineteen-seventies filmmaking. It has a wildness, a madness that is missing from Spielberg’s subsequent movies. The Disneyesque fireworks of the finale can’t hide the fact that the hero of the tale is abandoning his family in the grip of a monomaniacal obsession. Looking back, though, I’m sure that what really held me spellbound was the score, which, like that of “Star Wars,” was written by John Williams. I was a full-on classical-music nerd, playing the piano and trying to write my own compositions. I’d dabbled in Wagner, Bruckner, and Mahler, but knew nothing of twentieth-century music. “Close Encounters” offered, at the start, a seething mass of dissonant clusters, which abruptly coalesce into a bright, clipped C-major chord, somehow just as spooky as what came before. The “Star Wars” music had a familiar ring, but this kind of free, frenzied painting with sound was new to me, and has fascinated me ever since.

Now eighty-three years old, Williams remains a vital presence. “Star Wars: The Force Awakens,” his latest effort, is doing fairly good business, and he is at work on Spielberg’s next picture. He has scored all of the “Star Wars” movies, all of the Indiana Jones movies, several Harry Potters, “Jaws,” “E.T.,” “Superman,” “Jurassic Park,” and almost a hundred others. BoxOfficeMojo.com calculates that since 1975 Williams’s films have grossed around twenty billion dollars worldwide—and that leaves out the first seventeen years of his career. He has received forty-nine Oscar nominations, with a fiftieth almost certain for 2016. Perhaps his most crucial contribution is the role he has played in preserving the art of orchestral film music, which, in the early seventies, was losing ground to pop-song soundtracks. “Star Wars,” exuberantly blasted out by the London Symphony, made the orchestra seem essential again.

Williams’s wider influence on musical culture can’t be quantified, but it’s surely vast. The brilliant young composer Andrew Norman took up writing music after watching “Star Wars” on video, as William Robin notes in a Times profile. The conductor David Robertson, a disciple of Pierre Boulez and an unabashed Williams fan, told me that some current London Symphony players first became interested in their instruments after encountering “Star Wars.” Robertson, who regularly stages all-Williams concerts with the St. Louis Symphony, observed that professional musicians enjoy playing the scores because they are full of the kinds of intricacies and motivic connections that enliven the classic repertory. “He’s a man singularly fluent in the language of music,” Robertson said. “He’s very unassuming, very humble, but when he talks about music he can be the most interesting professor you’ve ever heard. He’s a deep listener, and that explains his ability to respond to film so acutely.”

It has long been fashionable to dismiss Williams as a mere pasticheur, who assembles scores from classical spare parts. Some have gone as far as to call him a plagiarist. A widely viewed YouTube video pairs the “Star Wars” main title with Erich Wolfgang Korngold’s music for “Kings Row,” a 1942 picture starring Ronald Reagan. Indeed, both share a fundamental pattern: a triplet figure, a rising fifth, a stepwise three-note descent. Also Korngoldesque are the glinting dissonances that affirm rather than undermine the diatonic harmony, as if putting floodlights on the chords.

To accuse Williams of plagiarism, however, brings to mind the famous retort made by Brahms when it was pointed out that the big tune in the finale of his First Symphony resembled Beethoven’s Ode to Joy: “Any ass can hear that.” Williams takes material from Korngold and uses it to forge something new. After the initial rising statement, the melodies go in quite different directions: Korngold’s winds downward to the tonic note, while Williams’s insists on the triplet rhythm and leaps up a minor seventh. I used to think that the latter gesture was taken from a passage in Bruckner’s Fourth Symphony, but the theme can’t have been stolen from two places simultaneously.

Although it’s fun to play tune detective, what makes these ideas indelible is the way they’re fleshed out, in harmony, rhythm, and orchestration. (To save time, Williams uses orchestrators, but his manuscripts arrive with almost all of the instrumentation spelled out.) We can all hum the trumpet line of the “Star Wars” main title, but the piece is more complicated than it seems. There’s a rhythmic quirk in the basic pattern of a triplet followed by two held notes: the first triplet falls on the fourth beat of the bar, while later ones fall on the first beat, with the second held note foreshortened. There are harmonic quirks, too. The opening fanfare is based on chains of fourths, adorning the initial B-flat-major triad with E-flats and A-flats. Those notes recur in the orchestral swirl around the trumpet theme. In the reprise, a bass line moves in contrary motion, further tweaking the chords above. All this interior activity creates dynamism. The march lunges forward with an irregular gait, rugged and ragged, like the Rebellion we see onscreen.

This is not to deny that Williams has a history of drawing heavily on established models. The Tatooine desert in “Star Wars” is a dead ringer for the steppes of Stravinsky’s “The Rite of Spring.” The “Mars” movement of Holst’s “Planets” frequently lurks behind menacing situations. Jeremy Orosz, in a recent academic paper, describes these gestures as “paraphrases”: rather than quoting outright, Williams “uses pre-existing material as a creative template to compose new music at a remarkable pace.” There’s another reason that “Star Wars” contains so many near-citations. At first, George Lucas had planned to fill the soundtrack with classical recordings, as Stanley Kubrick had done in “2001.” The temp track included Holst and Korngold. Williams, whom Lucas hired at Spielberg’s suggestion, acknowledged the director’s favorites while demonstrating the power of a freshly composed score. He seems to be saying: I can mimic anything you want, but you need a living voice.

In that delicate balancing act, Williams may have succeeded all too well. After “Star Wars,” he became a sound, a brand. The diversity and occasional daring of the composer’s earlier work—I’m thinking not only of “Close Encounters” but also of Robert Altman’s “Images” and “The Long Goodbye” and of Brian De Palma’s “The Fury”—subsided over time. Williams invariably achieves a level of craftsmanship that no other living Hollywood composer can match; his fundamental skill is equally evident in his sizable catalogue of concert-hall scores. Yet he’s been boxed in by the billions that his music has helped to earn. He has become integral to a populist economy on which thousands of careers depend.