Folk music is a very wide-open term. The origins of it are mostly unknown in most parts of the world, but traditional folk music was usually quite simple. There were only very simple changes in pitch; often binary or ternary or none at all. These are simple enough to where a person could intuitively grasp the calculations in their head (by counting the tempo and arrangement of percussive hits); even if they could not express them in written form. Later forms of folk music were derived from western classical music which definitely did require a lot of complex calculation.