Jazz comes in a wide variety of styles, and has several defining features. The most important of these is improvisation. Jazz musicians do not follow a set piece of music note by note, but make up melodies and chord changes as they play. Such improvisation is based on a musician's creative impulses, and is often inspired by interactions with the other players or the audience. It is this energetic feedback and element of anticipation that gives jazz its incredible dynamism. A piece is never played the same way twice.