Rock and roll (often written as rock & roll or rock 'n' roll) is a genre of popular music that originated and evolved in the United States during the late 1940s and early 1950s from musical styles such as gospel, jump blues, jazz, boogie woogie, and rhythm and blues, along with country music. While elements of what was to become rock and roll can be heard in blues records from the 1920s and in country records of the 1930s, the genre did not acquire its name until 1954.
According to Greg Kot, "rock and roll" refers to a style of popular music originating in the U.S. in the 1950s prior to its development by the mid-1960s into "the more encompassing international style known as rock music, though the latter also continued to be known as rock and roll." For the purpose of differentiation, this article deals with the first definition.
In the earliest rock and roll styles, either the piano or saxophone was typically the lead instrument, but these instruments were generally replaced or supplemented by guitar in the middle to late 1950s. The beat is essentially a dance rhythm with an accentuated backbeat, which is almost always provided by a snare drum. Classic rock and roll is usually played with one or two electric guitars (one lead, one rhythm), a double bass or string bass or (after the mid-1950s) an electric bass guitar, and a drum kit.
Beyond simply a musical style, rock and roll, as seen in movies, in fan magazines, and on television, influenced lifestyles, fashion, attitudes, and language. In addition, rock and roll may have contributed to the civil rights movement because both African-American and white American teenagers enjoyed the music. It went on to spawn various genres, often without the initially characteristic backbeat, that are now more commonly called simply "rock music" or "rock".