Usually it's a question of whether the music will be functional or subjective. If you have a love scene and the scene doesn't work and there's no electricity between the actors, the music might be called on to be romantic or emotional. But if the scene is very emotional and there's a lot of electricity between the actors, all the music really has to do is indicate to the audience that it's inappropriate to laugh. I know that's violent, but there's a point to this. Don't worry, we'll get there.
Music helps lead the audience through the mayhem, as opposed to creating the mayhem.
Yes, the classic example is a car chase. I contend the best car chases don't have music. Look at Billy Friedkin's movies, all those giant car chases have no music. The reason why is you've got screeching tires all over the place. You definitely can't turn down the sounds of screeching brakes and cars smashing into each other.