If for no other reason, people need to see Star Wars for its score. The film's score is so crazy-memorable that the American Film Institute lists it #1 of the 25 Greatest American Films Scores of all time.
It's become such a part of our cultural consciousness that we wager more people know the Star Wars title theme than most classical music pieces. If we asked you to hum Fur Elise, you might be stuck. But the Imperial March from Star Wars? Even a baby can do that.
The man behind the music is John Williams, and if you've seen a movie, chances are you've heard a John Williams score. Before Star Wars, Williams scored Jaws (1975), The Poseidon Adventure (1972), and won an Academy Award for Fiddler on the Roof (1971). His other credits include Superman (1978), Home Alone (1990), Jurassic Park (1993), the Indiana Jones series, other Star Wars films, and much, much more. The man is prolific.
Williams tends to favor orchestral scores—in fact, Star Wars was his first time working with the London Symphony Orchestra—and his work leans toward the classical, using music to underline the emotion of the scene.
Princess Leia's Theme uses violins and light winds to convey the gentleness of the character and the hope central to her struggle against the Empire. Conversely, the Death Star's theme uses trumpets and drums—instruments associated with war and the military—for a really foreboding musical queue. When the Millennium Falcon is being dragged into the battle station, the music informs you how much they don't want to go in there.
During the chasm crossfire scene, the upbeat tempo brings the excitement as Luke and Leia fight with seemingly no escape route. Then the music swells to a triumphant crescendo as the two swing across the chasm to safety. Likewise, during Luke's Death Star trench run, the music builds in suspense as Darth Vader hunts Luke, but pauses for some uplifting strings when Luke remembers Obi-Wan's soon-to-be-patented words of wisdom.
The score also helps Star Wars live on… and not just as a relic of the 1970's. Can you imagine a disco score for the Mos Eisley Cantina or the Death Star offensive? No matter your opinion on disco that just seems… wrong.