Improvisation in dance ranges from the widespread practice of contact improvisation, which involves interpersonal exploration of physical weight sharing and balance, through forms of structured and task-based improvisation, to the more controlled dance-generating systems in which source materials, tasks and rules of interaction are predefined. In dance for the stage, improvisation is often used as a method to create new movement material, which then is refined and set in repeatable choreography. However, an improvisation score or system can also be presented as performance, either by itself or in combination with set movement sections. Dance improvisation is, furthermore, commonly used as a form of somatic therapy and as a teaching tool.