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, primarily from a combination of African-American genres such as blues, jump blues, jazz, and gospel music, together with Western swing and country music. Though elements of 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 the 1950s.
The term “rock and roll” now has at least two different meanings, both in common usage: referring to the first wave of music that originated in the US in the 1950s and would later develop into the more encompassing international style known as “rock music”, and as a term simply synonymous with the rock music and culture in the broad sense. For the purpose of differentiation, this article deals with the first definition.
In the earliest rock and roll styles of the late 1940s and early 1950s, either the piano or saxophone was often the lead instrument, but these were generally replaced or supplemented by guitar in the middle to late 1950s. The beat is essentially a blues rhythm with an accentuated backbeat, the latter 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 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 and on television, influenced lifestyles, fashion, attitudes, and language. It went on to spawn various sub-genres, often without the initially characteristic backbeat, that are now more commonly called simply “rock music” or “rock”.
(Wikipedia contributors. “Rock and roll.” Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 8 Aug. 2014. Web. 11 Aug. 2014.)