Hip-hop is considered an important step in the history of music because, for the first time, non-tonal aspects of speech, its emphasis and lyricism, are the most identifiable aspects of vocalizations. Also, syncopation (when the accent is moved away from the strong beat) and abstract rhythms are also being used in ways never before. Hip-hop began as an idea during the 1970s, became a mainstream genre during the 1980s, and a internationally popular genre during the 1990s and 2000s. It is usually divided into three periods: Roots, Old School, and Golden Age. Most agree that the "golden age" ended during the 1990s. The current period is not yet named, though it is commonly referred to as New school hip hop.
Hip hop began in The Bronx, New York City when DJs began isolating the percussion break from funk and disco songs. By 1979, hip hop had become a commercially popular music genre and began to enter the American mainstream. In the 1990s, a form of hip hop 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. Hip hop arose during the 1970s at block parties in New York City
Early hip hop rhythms and (sampled) riffs were derived essentially from funk music.
As hip hop became popular, performers began speaking while the music played, and became known as MCs or emcees.
In 1979, the first commercially issued hip hop recordings were released: "Rapper's Delight" by The Sugarhill Gang which became a Top 40 hit on the U.S. Billboard pop singles chart.
In the late 1980s, a number of new hip hop styles and subgenres began appearing as the genre gained popularity. Hip hop musicians collaborated with rock bands and spread out into the genres of conscious hip hop, jazz-rap and gangsta rap.
According to the U.S. Department of State, hip hop is "now the center of a mega music and fashion industry around the world," that crosses social barriers and cuts across racial lines.