Following the turbulent political, social and musical changes of the 1960s and early 1970s, rock music diversified. What was formerly a discrete genre known as "rock and roll" evolved into a catchall category called simply "rock music", which came to include diverse styles developed in the US like punk rock. During the 1970s most of these styles were evolving in the underground music scene, while mainstream audiences began the decade with a wave of singer-songwriters who drew on the deeply emotional and personal lyrics of 1960s folk rock. The same period saw the rise of bombastic arena rock bands, bluesy Southern rock groups and mellow soft rock stars. Beginning in the later 1970s, the rock singer and songwriter Bruce Springsteen became a major star, with anthemic songs and dense, inscrutable lyrics that celebrated the poor and working class.