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 teens 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".
The phrase "rocking and rolling" originally described the movement of a ship on the ocean, but was used by the early twentieth century, both to describe the spiritual fervor of black church rituals and as a sexual analogy. Various gospel, blues and swing recordings used the phrase before it became used more frequently – but still intermittently – in the 1940s, on recordings and in reviews of what became known as "rhythm and blues" music aimed at a black audience.