Hip hop music is a genre of music typically consisting of a rhythmic style of speaking called rap over backing beats performed on a turntable by a DJ. Hip hop music is part of hip hop culture, which began in New York City in the 1970s, predominantly among African Americans and Latinos (two other elements are breakdancing and graffiti art). The term rap is sometimes used synonymously with hip hop music, though it originally referred only to rapping itself. Rapping, also referred to as MCing or emceeing, is a vocal style in which the performer speaks rhythmically and in rhyme, generally to a beat. Beats are traditionally sampled from portions of other songs by a DJ, though synthesizers, drum machines, and live bands are also used, especially in newer music. Rappers may perform poetry which they have written ahead of time, or improvise rhymes on the spot. Though rap is usually an integral component of hip hop music, DJs sometimes perform and record alone, and many instrumental acts are also defined as hip hop. Hip hop arose in New York City when DJs began isolating the percussion break from funk or disco songs for audiences to dance to. The role of the MC was originally to introduce the DJ and the music, and to keep the audience excited. The MC would speak between songs, giving exhortations to dance, greetings to audience members, jokes and anecdotes. Eventually, this practice became more stylized, and came to be 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 by some as promoting violence, promiscuity, drug use and misogyny. Nevertheless, by the beginning of the 2000s, hip hop became a staple of popular music charts and is now performed in widely varying styles around the world.