1.alternative rock: rock that has not yet crossed over into the mainstream, nirvana.
2.experimental rock, rock desgined to expand the boundarys of rock, yoko ono
3. hard rock, rock with a very heavy backbeat, screaming guitar chords, and an indecipherable vocalist, the rolling stones.
4.soft rock, innofensive, commercial rock, eventually branched off into pop, the who.
author: to each man his own, there are some extremely talented rappers and poppers.