Rock and roll (often written as rock & roll or rock 'n' roll) is a form of music that evolved in the United States in the late 1940s and early 1950s. Its roots lay mainly in blues, rhythm and blues, country, folk, gospel, and jazz. The style subsequently spread to the rest of the world and developed further, leading ultimately to modern rock music.

The term "rock and roll" now covers at least two different meanings, both in common usage. The American Heritage Dictionary and the Merriam-Webster Dictionary both define rock and roll as synonymous with rock music. Conversely, Allwords.com defines the term to refer specifically to the music of the 1950s. For the purpose of differentiation, this article uses the latter definition, while the broader musical genre is discussed in the rock music article.

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. 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 boogie woogie blues rhythm with an accentuated backbeat, the latter almost always provided by a snare drum.

The massive popularity and eventual worldwide view of rock and roll gave it a unique social impact. Far beyond simply a musical style, rock and roll, as seen in movies and in the new medium of 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".

Origins of the style

Main: Origins of rock and roll The immediate origins of rock and roll lie in the late 1940s and early 1950s, when various popular musical genres of the time - including blues, country music, rhythm and blues, folk music and gospel music - combined to give rise to the new style.

However, elements of rock and roll can be heard in many "hillbilly" and "race music" records of the 1920s and 1930s. This music was often relegated to "race music" outlets (as rhythm and blues stations were referred to at the time) and was rarely heard by mainstream white audiences. A few black rhythm and blues musicians, notably Louis Jordan, the Mills Brothers, and The Ink Spots, achieved crossover success; in some cases (such as Jordan's "Choo Choo Ch'Boogie") this was achieved with numbers composed by white songwriters. The Western swing genre in the 1930s, generally played by white musicians, also shared similarities with rock and roll, and in turn directly influenced rockabilly and rock and roll, as can be heard (for example) on Elvis Presley's rendition of "Jailhouse Rock" (1957).

Going back even further, rock and roll can trace one lineage to the old Five Points, Manhattan district of mid-19th century New York City, the scene of the first fusion of heavily rhythmic African shuffles and sand dances with melody-driven European genres, particularly the Irish jig. As Alan Freed states in the 1956 film Rock, Rock, Rock, "1ock and roll is a river of music that has absorbed many streams: rhythm and blues, jazz, rag time, cowboy songs, country songs, folk songs. All have contributed to the big beat."