Until the 20th century, most ballroom dances were sequence dances. The way people moved was planned in set formation. These formations were usually lines or squares. Everyone moved at the same time, and finished at the same time. The music played for a set time, and then stopped. After the invention of the waltz, around 1800, another style of dancing developed. In the waltz, and later dances, people danced in couples, but they did so separately. They did not dance in formation, but moved round the room as they pleased (but anti-clockwise). Often, new dance styles arrive. Some dance as individuals, separately, as they please. Street dance is like that. All these types of dance have music.