Modern ballroom dance has its roots early in the 20th century, when several different things happened more or less at the same time. The first was a movement away from the sequence dances towards dances where the couples moved independently. This had been pre-figured by the waltz, which had already made this transition. The second was a wave of popular music, such as jazz. Since dance is to a large extent tied to music, this led to a burst of newly invented dances. There were many dance crazes in the period 1910–1930.