As I mentioned in the post below, when putting together a film, the palette you use and the music you choose are the most important tools for making the audience feel the way you want them to feel from scene to scene. As I said, a dark palette will make your audience feel one way and a bright palette will make them feel another, just as a palette of cold colors will give one feeling to the viewer and one of warm colors will give a different feeling.
Anyway this is far from a hard-and-fast rule, of course, and there are plenty of contrary examples. Sometimes contrast is your greatest tool: for example, if your character is depressed, putting him in the middle of a colorful birthday party may make him seem all the more depressed by contrast, and may work even better than putting him in a gray room on a rainy day.
Anyway here are some screengrabs that I got from this great site: As you look at each one, think about the feeling you get from each based on the colors used. It's easy to see why so may film makers exploit the way color and tone can help amplify the feeling they are trying to communicate.
Music functions the same way; the musical soundtrack is very helpful at getting the audience into the mood that you want them to experience. We all know what it's like when they show a trailer at the movies and that sweeping, epic music kicks in...we know exactly what type of movie they're selling and what type of emotion we'll get from that movie. And then think about when you see a trailer for a comedy, and think about the kind of music that usually kicks in...a light, jaunty kind of number that makes the movie feel light and fun. So in the minute or so that the studio has to sell you on the idea of the movie they use music to help sell the type of feeling the movie will have when you go see it. Imagine what it would be like if the type of music in the trailer was reversed, if a trailer for a movie like "Revolutionary Road" had light and bouncy music, or if the trailer for "Hotel for Dogs" had big sweeping music that sounded like it came from "Braveheart" or something. The contrast would probably have a confusing effect, although it might also be pretty funny.
If I had the time and/or the resources I would love to take clips from movies and re-cut them with different music. Definitely if I taught a film class I would do that, it would really be informative to experiment around with that. Maybe somebody on the Internet has already done this and somebody could point us all in that direction.
That's one of the most interesting parts of animated film production - when you're assembling the story reels, cutting together the storyboards with the temp dialogue, sound effects and temp music - culled from other soundtrack CDs, of course - it's really a great opportunity to see how different music can affect the feel of the storyboards. The wrong music can really keep the boards from succeeding. A lot of times the music is too far one way and it feels like the music is trying to oversell the emotion of the scene. If the music is bigger and more dramatic than the moment deserves, the music calls attention to itself and the sequence feels false because the film hasn't earned it at that spot.
Making films is all about manipulating the audience and getting them to react to your story and characters in the way you want them to react. But if the audience becomes aware of what you are trying to do to manipulate them then it won't work and they won't have the emotional reaction you want them to have. It can be very easy to overplay your hand and ruin the effect you're trying to accomplish.