Musical improvisation (also known as musical extemporization) is the creative activity of immediate ("in the moment") musical composition, which combines performance with communication of emotions and instrumental technique as well as spontaneous response to other musicians. Sometimes musical ideas in improvisation are spontaneous, but may be based on chord changes in classical music, and many other kinds of music. One definition is a "performance given extempore without planning or preparation." Another definition is to "play or sing (music) extemporaneously, by inventing variations on a melody or creating new melodies, rhythms and harmonies."