Musical movement.
In the mid 1960s the popularity of a number of British rock-and-roll ("beat") groups spread rapidly to the U.S., beginning with the triumphant arrival of Liverpool's Beatles in New York in 1964 and continuing with the Rolling Stones , the Animals, and others. Building on 1950s U.S. models, these groups incorporated such local musical traditions as skiffle (acoustic drummerless ensembles), dancehall, and Celtic folk.