Music is an art form whose medium is sound. The common elements of music are pitch (which governs melody and harmony), rhythm (and its associated concepts tempo, meter, and articulation), dynamics, and the sonic qualities of timbre and texture. Music has been around since the dawn of time. From the first tribal dances to the newest and strangest methods being used, the origins of rhythm can also be traced back to the dawn of time. Music can be divided into genres and subgenres, although the dividing lines and relationships between music genres are often subtle. To many people, in many cultures music is an important part of their way of life.