Impromptu music is an unplanned and spontaneous form of music-making that brings joy and creativity. There are various synonyms for impromptu music. One is "jamming," which refers to the act of playing music together in an improvisational and spontaneous way. Another synonym is "freestyle," which typically implies a more individualistic approach to impromptu music-making. "Unrehearsed" is another word that could describe impromptu music as it emphasizes the lack of preparation and planning involved in this type of music-making. Lastly, "spontaneous" captures the essence of the impromptu music, emphasizing the improvisation and creativity that characterizes this unique form of musical expression.