Despite the slightly ridiculous-looking title character, Jaws is a great movie. It’s got great pacing, great acting, great editing, great cinematography, and particularly, great directing, uniting Hitchcock’s suspense with Ford’s characterization, Hawks’ dialogue, and Curtiz’s energy in one irresistible package. Jaws, which returns to the Michigan Theater on Aug. 5 & 7, was a sensation in 1975. It was the first of the summer blockbusters, and the work that announced Stephen Spielberg as one of the great Hollywood filmmakers—and it’s still a hell of a thrill now.

But the best thing, the most memorable thing, and possibly the single coolest thing about the movie—the thing that distills the movie’s suspense to its quintessence, the thing that has so thoroughly permeated popular culture that young folks know it before they see the movie—that thing, ladies and gentlemen, can be summed up in a single onomatopoetic word: BA-Dum.

When that two-note motive sounds deep down in the double basses, you know dread. And as the tempo quickens and the volume increases, you know fear. And as the percussion pound ominously, the tuba winds sinuously, the strings swell soulfully, and the winds pipe poignantly, you know terror. A monster’s coming—and it won’t stop.

That’s the genius of John Williams. Just two notes and you’re already afraid.

Williams learned how to compose from Mario Castelnuovo-Tedesco while at UCLA, learned to play the piano from Rosina Lhévinne while at Julliard, and learned to orchestrate from the three wise men of Hollywood film scores: Franz Waxman, Bernard Herrmann, and Alfred Newman. But he made his first deep mark on popular culture playing piano in Henry Mancini’s studio orchestra when they cut the soundtrack for the TV show Peter Gunn. That cat beating boogie-woogie piano? That’s “Johnny” aka “Little Johnny Love” Williams.

Though there are other great film score composers working now, Williams has truly defined the genre for the last thirty-five years. He wrote the scores for not just all Spielberg’s movies (including the upcoming Lincoln), and all the Star Wars movies, all the Indiana Jones movies, all the Superman movies, all the Jurassic Park movies, and all the Harry Potter movies, but also the scores for JFK, Nixon, and, yes, Valley of the Dolls.

Without Williams’ score, the opening shark attack in Jaws would be just some blond being whipped back and forth in a water tank, and the climactic chase would be just three dudes in a boat towing three yellow barrels. But with Williams’ music, those sequences are among the most exciting in cinema.