Movement of music that started essentially with the heavy rock movements of such bands as but not limited to: The Cream, The Spiders, Iron Butterfly, The Jimi Hendrix Experience, Led Zepplin, and Kiss. The sound took a larger heavier sound with bands like Aerosmith, Black Sabbath, Pentagram, AC/DC and such bands. But Black Sabbath was the most respected and possibly the darkest of the lot. This is considered the Classical Metal era between the mid sixties to the late seventies. From there on out, when the eighties rolled around, Speed metal became popular with the NWOBHM movement, and thrash metal evolved with such bands as Metallica, Exodus, Primus, Trauma, Megadeth, Testament et cetera. During the 80s a more underground movement of slow metal began to evolve called Doom Metal by such bands as Candlemass, Pentagram and the like. Also in the mid 80s a new form of metal evolved from thrash called Death Metal, and used screams, and heavy notes, and shortly after a new style formed yet again from death metal called grind metal or grindcore. The 90's rolled around, and Groove Metal began evolving with such bands as Pantera, and even Ozzy with his new guitarist took upon himself a slower style more groove/doom based rather than thrash. Then around the late 90s the groove and doom metal scene flourished and produced such bands as crowbar, down, and black label society. Also around the 90s a new form of Metal formed, New Metal. It comprised of such bands as Korn, Slipknot, System of a Down, Tool, Nine Inch Nails, Manson, Sevendust, and Godsmack. This style focuses on dissonance for heaviness and loud vocals, probably inspired by the death/noisecore of the late 80's movement.