Hip hop music is a style of popular music. It is usually composed of two elements: rapping (also known as emceeing) and DJing. When combined with breakdancing and graffiti art, these are the four components of hip hop, a cultural movement which began in New York City in the 1970s, predominantly by African Americans and Latinos. The term rap music is sometimes used synonymously with hip hop music, though it is also used to refer specifically to the practice of rapping.
Typically, hip hop music consists of one or more rappers who chant semi-autobiographic tales, often relating to a fictionalized counterpart, in an intensely rhythmic lyrical form, making abundant use of techniques like assonance, alliteration, and rhyme. Though rap may be performed a cappella, it is more common for the rapper(s) to be accompanied by a DJ or a live band providing an appropriate beat. This beat is often from the percussion of a different song, usually rock, funk, or soul, and is sometimes sampled. In addition to the beat, other sounds are often sampled, synthesized, or performed. Though rap is usually an integral component of hip hop music, instrumental and non-rap Electro acts such as Planet Patrol are also defined as hip hop music groups.
Hip hop arose in New York City when DJs began isolating the percussion break from funk or disco songs. The role of the emcee (MC) arose to introduce the DJ and the music, and to keep the audience excited. The MCs began by speaking between songs, giving exhortations to dance, greetings to audience members, jokes and anecdotes. Eventually, this practice came to be more stylized, and was known as rapping. By 1979, hip hop had become a commercially recorded music genre, and began to enter the American mainstream. It also began its spread across the world. In the 1990s, a form called gangsta rap became a major part of American music, causing significant controversy over lyrics which were perceived as promoting violence, promiscuity, drug use and misogyny. Nevertheless, by the beginning of the 2000s, hip hop was a staple of popular music charts and was being performed in many styles across the world.