Reggae music is relatively young in the scope of world music having started in the 1950s. It grew out of political and social upheavals of the Caribbean in the 1950s, and became the "sound" of Jamaica by the 1970s. Some reggae stars, notably Bob Marley, became crossover standouts who influenced musicians of many other genres.
According to Reggae.com, reggae derived from Jamaican musicans who mixed the calypso, rhythm and blues and ska they heard on American and Caribbean records and radio. The basic core of reggae is the tightly-synchronized bass and drum rhythms with staccato guitar strums with a "one drop" feel. The musicians avoid playing on beat one and instead emphasize beat three in a normal bar of 4/4 timing. A typical reggae song has a slow to medium tempo. Even dance songs tend to be driven by repetition of rhythms and thick bass lines instead of a fast drum beat like most rock and pop music.
The most significant event in the history of reggae may have been the founding of Island Records by Chris Blackwell in 1960. Blackwell gave the local artists a place to record this new style, and he promoted it more when the label relocated to London in 1962. It wasn't until the next decade that reggae produced true crossover stars. The cult hit movie "The Harder They Come" from 1972 featured reggae star Jimmy Cliff in the lead role and four of his songs, including the title tune. It was the first major exposure most pop fans had to reggae and its culture. Bob Marley and the Wailers started in 1963 when Marley was in his teens. The band made it into the 70s as reggaes top act and a concert draw on par with most of the day's top pop acts. Reggae hit its first peak of popularity in the mid 70s after Eric Clapton scored a big hit with Marley's "I Shot the Sheriff," and "Rolling Stone" declared the Wailers its band of the year for 1976.
According to Scaruffi.com reggae has splintered and developed into many sub-genres. "Dub" has vocals resembling rap. "Dancehall" is aimed at dance clubs. "Reggae fusion" combines elements of both reggae and jazz and "Reggaeton" is an upbeat variant that involves rapping and singing and is very popular for dancing.
Reggae has long been a vessel for its musicians to express political and social views. Most notably it's been tied to the Rastafari movement. While it promotes peace and love, it also espouses the spiritual use of cannabis and some Afro-centric political believes. Marley became a symbol for both the music and Rastas (his 1976 album was called "Rasta Man Vibration') and it may have made him a political target. He survived a shooting in 1976 just days before a concert intended to promote peace between rival factions in Jamaica.
Marley died of cancer in 1981, but as of 2010 he remains a cherished figure among reggae fans. His songs have been covered by many artists in many genres, and Jamaica's tourism campaign of 2009 featured a version of Marley's "One Love." Marley was inducted into the Rock and Roll Hall of Fame in 1994. Cliff and Blackwell are the only other reggae notables in the hall as of 2010.