By 1979 hip hop music had become a mainstream genre. It spread across the world in the 1990s with controversial "gangsta" rap. Herc also developed upon break-beat deejaying, where the breaks of funk songs—the part most suited to dance, usually percussion-based—were isolated and repeated for the purpose of all-night dance parties. This form of music playback, using hard funk and rock, formed the basis of hip hop music. Campbell's announcements and exhortations to dancers would lead to the syncopated, rhymed spoken accompaniment now known as rapping. He dubbed his dancers "break-boys" and "break-girls," or simply b-boys and b-girls. According to Herc, "breaking" was also street slang for "getting excited" and "acting energetically"