Music is an art form, a cultural activity, and a medium of sound. General definitions of music include common elements such as pitch (which governs melody and harmony), rhythm (and its related concepts, rhythm, meter, and expressiveness), dynamics (loudness and softness), and the vocal qualities of timbre and texture (sometimes called the "colour" of a musical sound). Different styles or genres of music may emphasize, de-emphasize, or omit some of these elements. Music is played using a wide variety of instruments and vocal techniques ranging from vocals to rap. There are music-only pieces, vocal-only pieces (such as songs without instrument accompaniment) and pieces that combine vocals and instruments. The word is derived from the Greek μουσική (mouse; "the art of inspiration"). See a glossary of musical terms.