Two notes, alternating, slowly speeding up — and audiences who've never taken a music lesson instantly know a shark is close, before the camera shows anything at all. John Williams's theme for Jaws (1975) is one of the most famous examples of a much older technique: the leitmotif, a short, recognisable musical phrase used to represent a character, place, or threat, doing emotional work a visual cue alone can't manage as quickly.
A technique borrowed from opera, built for the screen
Leitmotif as a formal device is most associated with Richard Wagner's nineteenth-century operas, where specific musical phrases recur whenever a particular character, object, or idea appears, letting the orchestra comment on and foreshadow the drama independently of what's actually being sung. Film composers adapted the same logic to a medium where music can run almost continuously under dialogue and action. Williams's own recurring character themes across the Star Wars saga are a later, famous example of the same idea: a few bars of music doing the narrative work of a paragraph of exposition.
Why the Jaws theme works even stripped down to almost nothing
The shark theme itself is deliberately minimal — two alternating notes, a half-step apart, played low in the strings, that speed up as the perceived threat closes in. That simplicity is part of the design. A theme this stripped-down can be recognised instantly, layered subtly under other sound without competing for attention, and sped up or slowed down in real time to track rising tension in a way a longer, more melodically complex theme couldn't manage nearly as cleanly.
What we're still unsure about
Exactly why certain simple musical patterns — a tense half-step interval, an accelerating rhythm — reliably read as threatening across such a broad range of listeners isn't fully settled between two competing explanations. One points to learned cultural association: decades of film and television have trained audiences to link these specific patterns with danger through sheer repeated exposure. The other points to something closer to a built-in acoustic response, arguing certain sound qualities overlap with distress or warning signals our auditory system may be primed to flag regardless of cultural exposure. Disentangling how much of a film score's emotional effect is learned convention versus something closer to a hardwired response remains an open question in music psychology.
This sits inside Film & Media Scoring, one of seven topics in Composition, one of four domains in Music, one of seventeen subjects the app can quiz you on.