Music changed with the world following World War II. The next three decades were shadowed by the Cold War and Vietnam, by social conflict, and by rapid technological change. Jazz, country, bluegrass, folk, Broadway musicals, and film scores all reflected the moods of the times, and in the mid-1950s, rock & roll grew out of that rich musical diversity to transform popular culture forever. The artists who defined the era — Frank Sinatra, Elvis Presley, Johnny Cash, Patsy Cline, The Beatles, Bernard Herrmann, Leonard Bernstein, John Coltrane, and Bob Dylan, among many others — remain touchstones to this day, and many of their songs remain popular today.