Folk rock: Folk rock, hybrid musical style that emerged in the United States and Britain in the mid-1960s. As the American folk music revival gathered momentum in the 1950s and ’60s, it was inevitable that a high-minded movement that prided itself on the purity of its acoustic instrumentation and its Mumford & Sons, West London indie rock quartet, have created a gutsy, old-time sound that marries the magic of Crosby,…