This is (among other things) an attempt to use musical themes to represent certain factions, a la John Williams. The heroic main theme represents the humans, and it makes multiple appearances each time they come on screen. But if you listen closely you can hear that not all is well with this particular group of humans. Very early in the video, for example, you’ll hear the change in the melody that coincides with the revelation that the beasts they are subduing are actually a family. The humans clearly see them as sub-human, which sets the stage for the rest of the story.