Any music that has a regular pulse can cause listeners to tap their feet or clap in unison. Sometimes, however, such coordination of physical activity is the primary purpose of music. This is the case when soldiers sing together while they march, or when a DJ blasts music onto a crowded dance floor. Work songs can coordinate practical labor, such as chopping wood or sowing seeds, while dance music brings people together in an enjoyable social activity. All music related to movement, however, has certain elements in common, for it must relate to the mechanical functions of the human body.