Following the turbulent political, social and musical changes of the 1960s and early 1970s, rock music diversified. What was formerly known as "rock and roll", a reasonably discrete style of music, had evolved into a catchall category called simply "rock music", an umbrella term which would eventually include diverse styles like heavy metal music, punk rock and, sometimes even hip hop music. During the 1970s, however, most of these styles were not part of mainstream music, and were evolving in the underground music scene.