The sound of closing doors, footsteps, and explosions is important, but what about the slow, sad music during the funeral scene? Or the majestic marching tune when the soldiers go off to war? Or the creepy, eerie tune when the child is lost in the woods? Music in the background of a movie is just as important.
Movies use music in a lot of ways you may never have even noticed. John Carpenter is a director who makes and produces the music for just about all of his movies. "You shouldn't be aware of what I'm doing ... You shouldn't be sitting there listening to music, or aware of it ... I don't want you to be aware of the technique. I just want you to feel it." However, movie-goers of this day and age have learned to recognize the techniques. When King Kong climbs the Empire State Building, it's obvious that the music is slowly going upward.
Another good technique to use with sound tracks is the concept of every character having his or her own song or theme. This idea can be clearly scene in the Star Wars movies. To the average observer, all of a villains quite obviously have a theme, but actually the protagonists have their own subtle themes as well. Watch it sometime and see for yourself
(Information taken from http://filmsound.org/articles/horrorsound/horrorsound.htm)