Rock music typically uses simple unsyncopated rhythms in a 4/4 meter, with a repetitive snare drum back beat on beats two and four. Guitar solos feature prominently in rock music; however, keyboard, saxophone and blues-style harmonica are also sometimes used as soloing instruments. In its "purest form", it "has three chords, a strong, insistent back beat, and a catchy melody. Rock music is a genre of popular music that developed during and after the 1960s. It has its roots in 1940s and 1950s rock and roll, rhythm and blues, country music and also drew on folk music, jazz and classical music. The sound of rock often revolves around the electric guitar, bass guitar, drums, and keyboard instruments such as Hammond organ, piano, or, since the late 60s, synthesizers.
In the late 1960s and early 1970s, rock music developed different subgenres. When it was blended with folk music it created folk rock, with blues to create blues-rock and with jazz, to create jazz-rock fusion. In the 1970s, rock incorporated influences from soul, funk, and Latin music. Also in the 1970s, rock developed a large number of subgenres, such as soft rock, glam rock, heavy metal, hard rock, progressive rock, and punk rock. Rock subgenres that emerged in the 1980s included New Wave, hardcore punk and alternative rock. In the 1990s, rock subgenres included grunge, Britpop, indie rock, and nu metal.
A group of musicians specializing in rock music is called a rock band or rock group. Many rock groups consist of an electric guitarist, lead singer, bass guitarist, and a drummer, forming a quartet.
Some groups omit one or more of these roles or utilize a lead singer who plays an instrument while singing, sometimes forming a trio or duo; others include additional musicians such as one or two rhythm guitarists or a keyboardist.
Rock bands from some genres, particularly those related to rock's foundations in rock and roll, include a saxophone
More rarely, groups also utilize bowed stringed instruments such as violins or cellos, and brass instruments such as trumpets or trombones.
In the new millennium the term rock has been used as a blanket term including forms such as pop music, reggae music, soul music, and sometimes even hip hop, with which it has often been contrasted through much of its history
Punk rock was developed between 1974 and 1976 in the United States and the United Kingdom. Rooted in garage rock and other forms of what is now known as protopunk music, punk rock bands eschewed the perceived excesses of mainstream 1970s rock.They created fast, hard-edged music, typically with short songs, stripped-down instrumentation, and often political, anti-establishment lyrics. Punk embraces a DIY (do it yourself) ethic, with many bands self-producing their recordings and distributing them through informal channels
By late 1976, acts such as the Ramones and Patti Smith, in New York City, and the Sex Pistols and The Clash, in London, were recognized as the vanguard of a new musical movement. The following year saw punk rock spreading around the world. Punk quickly, though briefly, became a major cultural phenomenon in the United Kingdom. For the most part, punk took root in local scenes that tended to reject association with the mainstream. An associated punk subculture emerged, expressing youthful rebellion and characterized by distinctive clothing styles and a variety of anti- authoritarian ideologies.
By the beginning of the 1980s, faster, more aggressive styles such as hardcore and Oi! had become the predominant mode of punk rock. Since punk rock's initial popularity in the 1970s and the renewed interest created by the punk revival of the 1990s, punk rock continues to have a strong underground following. This has resulted in several evolved strains of hardcore punk, such as D-beat (a distortion-heavy subgenre influenced by the UK band Discharge), anarcho-punk (such as Crass), grindcore (such as Napalm Death), and crust punk. Musicians identifying with or inspired by punk also pursued a broad range of other variations, giving rise to New Wave, post- punk and the alternative rock movement