Your grandparents may remember the old silent Charlie Chaplin comedy films. If so, they'll probably tell you that without the music that accompanied them these films wouldn't be much fun.
Later, when films began to have sound, the music stayed because directors use pieces of music and sound to create particular moods and feelings. We call these musical cliches.
In horror films and thrillers, for example, loud sounds let you know when something frightening is going to happen. Violin tunes accompany emotional scenes in romantic films, and in adventure films we use sharp and fast sounds for action scenes.
Some musical cliches introduce specific places. Shots of Hong Kong, for example, often have xylophone music in the background while shots of Paris come with melodies played on the accordion. There are many musical cliches for a number of types of scenes.
So, next time you watch a film, pay attention to the music in the background. You'll be surprised how many musical cliches you can spot