In some ways, 2018 marks a noteworthy anniversary for the overture in cinema (though, to date, not a single wide release this year has featured one). It’s been half a century since Funny Girl and 2001: A Space Odyssey hit theaters; Ben Hur and North by Northwest premiered 60 years ago, Gone With the Wind nearly 80. Aside from their cultural significance, each of these films makes deliberate use of a graphic or instrumental prelude that sets the mood or establishes relevant themes—the lush musical score that precedes Civil War romance in Gone With the Wind, for example, or the Latin rhythms and pop-jukebox compilations set to bold color palettes in West Side Story. In some cases, the movie’s overture has become a showpiece itself.

“Opening sequences guide us into the dynamic and meaningful unfolding of an on-screen narrative,” writes Annette Insdorf, in one of the most comprehensive guides on the subject, Cinematic Overtures: How to Read Opening Scenes. The title sequence of a movie is often called an overture when it combines visual and musical elements, but the term is sometimes deployed loosely. Some critics argue that overtures allow the story to take shape, that they’re a sequence of images and sounds in which “the film reflects on ... the process of its own coming into being.” Others maintain that the device is strictly reserved for the razzmatazz of Broadway musicals, not the storytelling of highbrow drama—yet these preludes have historically been used to great effect in non-musicals.

From the old French une ouverture, meaning an opening, the film overture frequently signifies an introduction to something more substantial, but it can also mean an approach that establishes a relationship. 2001 does both: The wordless first 25 minutes of Kubrick’s 1968 masterpiece serve as both narrative prologue and as emissary from director to audience. Here, the sequence is an invitation that rewards active curiosity: Might the featureless screen be a metaphor for the monolith itself? Could the film’s pitch-black opening be an allegory for man’s place in the vast emptiness of the void? Is the cosmic crescendo of György Ligeti’s Requiem a stand-in for the universe just before the Big Bang and “the dawn of man”? While it’s much easier to ask such questions after the final credits have rolled, overtures prompt inquiry at the outset, urging audiences to climb aboard as voyeurs, skeptics, or simply passengers along for the ride.

What’s more certain is that overtures transformed over time, in concert with the changing experience of moviegoing. Newsreels and animated shorts, once a cinema staple, disappeared in the 1960s. To fill that gap (and lure people away from television’s increasing popularity), studios devised the roadshow: a prestige release format for big-budget films. Roadshows were longer and more expensive to produce than regular motion-picture screenings, but the viewing experience was singular. These traveling exhibitions featured live orchestras and reserved seating inside lavish theaters. Glittering marquees announced premieres in cities like New York or Los Angeles, where tickets sold well in advance. Since roadshows lasted hours, curtains were closed at each reel change (what we might now call an intermission), giving moviegoers a chance to buy concessions and providing a buffer for latecomers. Projectionists worked hard to get these cues and timings right, and audiences, for their part, understood them: Overtures marked the start of storytelling and spectacle.