ルーツ・ミュージック
Some believe that folk music originated as art music that was changed and probably debased by oral transmission while reflecting the character of the society that produced it. In many societies, especially preliterate ones, the cultural transmission of folk music requires learning by ear, although notation has evolved in some cultures. Different cultures may have different notions concerning a division between "folk" music on the one hand and of "art" and "court" music on the other. In the proliferation of popular music genres, some traditional folk music became also referred to as "World music" or "Roots music."