Rock music is a genre of popular music. It developed during and after the 1960s in the United Kingdom and the United States. It originally started in the 1940s and 1950s with the start of rock and roll. Rock and roll grew out of rhythm and blues and country music. Rock music is related to a number of other genres such as blues and folk. It has influences from jazz, classical and other music genres.
Musically, rock mostly uses the electric guitar as part of a rock group with bass guitar and drums. Rock music is song-based. It has a 4/4 beat and it has verse-chorus form. However, rock has become very different and it is hard to say what its common musical instruments are. Like popular music, rock music lyrics are mostly about "romantic love". They can also have social or have political themes, however. Rock focuses on musical skill, live performance, and it tries to be more real than pop music.
By the late 1960s, a number of different rock music below-genres had come out. These included hybrids like blues rock, folk rock, country rock, and jazz-rock fusion. From these forms, the counterculture developed psychedelic rock. New genres that came from this scene included progressive rock, glam rock and heavy metal. Progressive rock made the music more artistic. Glam rock focused on showmanship and what you can see. Heavy metal which focused on loudness, power and speed. In the second half of the 1970s, punk rock both intensified and reacted against some of these trends to produce a raw, energetic form of music characterized by overt political and social critiques. Punk caused other below-genres to come about into the 1980s, including New Wave, post-punk and eventually the alternative rock movement. From the 1990s, alternative rock began to be the most popular type of rock music. It broke through into the mainstream in the form of grunge, Britpop, and indie rock. More merging of below-genres have since emerged. These include pop punk, rap rock, and rap metal, as well as conscious attempts to revisit rock's history, including the garage rock/post-punk and synthpop revivals at the beginning of the new millennium.
Rock music has also helped cultural and social movements. This led to large sub-cultures including mods and rockers in the UK and the "hippie" culture that spread out from San Francisco in the US in the 1960s. Similarly, 1970s punk culture made the goth and emo subcultures. Rock music has the same folk tradition as the protest song. Rock music has been involved with political activism. It has also made changes to social attitudes towards race, sex and drug use. It is often seen as an expression of youth revolt against adult consumerism and conformity.