Rock music is a genre of popular music that developed during the 1960s, especially in Britain and the United States. In its roots it was influenced by the rock and roll of the 1940s and 1950s, and also heavily by rhythm and blues and country music. Rock Music is also indebted to a number of other genres such as blues and folk, and incorporates influences from jazz, classical and other musical sources.
Typically, rock is song-based music made with a 4 /4 beat using a verse-chorus, but the genre is extremely diverse and common musical characteristics are difficult to define.
In the late 1960s a number of distinct rock music sub-genres were created, including hybrids like blues-rock, folk rock, country rock, and jazz-rock fusion, many of which lead to the development of psychedelic rock of the counter-culture, which influenced the psychedelic scene. New genres that were offshoots from this scene were progressive rock, which extended the artistic elements, glam rock, which highlighted showmanship and visual style, and the diverse major sub-genre of heavy metal, which emphasized volume, power and speed.
In the second half of the 1970s, punk rock both intensified and reacted against some of these trends with a raw, energetic form of music to produce open political and social criticism. Punk was an influence into the 1980s on the subsequent development of other sub-genres, including New Wave, post punk and eventually the alternative rock movement.
From the 1990s alternative rock began to dominate rock music and to break into the mainstream in the form of grunge, Britpop, and indie rock. Further fusion sub-genres since emerged, including pop punk, rap rock and rap metal, as well as conscious attempts to revive once again rock history, including the garage rock / post-punk and synthpop revivals at the beginning of the new millennium.
Rock music has also embodied and served as a vehicle for cultural and social movements, leading to major sub-cultures such as the mods and rockers in the UK and the “hippie” counterculture that spread in the United States from San Francisco in the 1960s. Likewise, the 1970s punk culture spawned the visually distinctive goth and emo subcultures. In the tradition of the folk protest song, rock music was brought together with political activism as well as changes in social attitudes to race, sex and drug use, and is often seen as an expression of youth revolt against adult consumerism and conformity.
The sound of traditional rock is centered around the electric guitar, which emerged in its modern form in the 1950s once with the popularization of rock and roll . The sound of the guitar in rock music is typically supported by the electric bass guitar pioneered in jazz music at about the same time, and percussion produced from a drum kit that combines drums and cymbals. This trio of instruments has often been complemented by synthesizers and the inclusion of others, particularly keyboards such as piano, or the Hammond organ. A group of musicians that play rock music is a rock band or rock group, and typically consists of two to five members. Classically, a rock band takes the form of a quartet whose members play one or more roles, including vocalist, guitarist, bassist, drummer and occasionally that of keyboard player or another instrumentalist.