Music is an art form and cultural activity, and its medium is sound organized on time. The definition of general music includes common elements such as pitch (which governs melody and harmony), rhythm (and its associated conceptual rhythm, meters, and joints), dynamics (loudness and softness), and sound wave quality timbre and texture (This is sometimes called the "color" of the sound of music). Different styles or types of music may be emphasized, and some elements are not emphasized or ignored. Music is played using a variety of musical instruments and vocal techniques, from singing to rap; there are only instrumental works, only vocal works (such as songs without musical accompaniment) and works that combine singing and musical instruments. The word is derived from the Greek word μουσική (mousike; "Muse Art"). See music glossary.