One of the most memorable themes that I heard was the one from “JAWS.” Every time I hear those two introductory chords; it reminds me of something out there in the depths of the ocean that still exists and can truly devour you. Two more great ones are from the “Star Wars” and “Indiana Jones” franchises. “The Godfather” theme—well what can I say? Can you think of any others, I know there are numerous?
The first one that came to mind was the theme from "Mahogony," one of my favorite movies starring Diana Ross. But the iconic theme that is the best example for me of what you're asking for opens with four chords: the theme from "Close Encounters of the Third Kind." Who could ever forget that tune in their head?
I can never listen to music by Moby without thinking of the films his music has appeared in. In Atonement a hymn called "Dear Lord and Father of Mankind" is being sung at a panning scene as soldiers were leaving Dunkirk. It was a superb piece of cinematography and the music was so emotive.
Billy Elliot had a fantastic soundtrack, though I did not live through the time it was set- the music really gave you a sense of the times. It was also quite angst ridden which sat up well against the back drop of the miners strike and Thatcherite Britain.