A variety of punk rock originating in the US in the early '80s. It involves shouted vocals (as opposed to growled) with a fast, aggressive tempo and a guitar sound featuring quick chord changes. Minor Threat, Bad Brains, SSD, and the Circle Jerks are known for this style. By 1986, a new style of hardcore came out of the New York scene. The NYHC scene added mosh breakdowns to mix, but the music retained its fast aggressive nature. This spawned the youth crew scene, a positive straight edge scene featuring such bands as Youth of Today, Chain of Strength, and the Gorilla Biscuits. Judge is a notable band from this era that added some metal style to their riffs. In the 90s hardcore took many different direction, bands like Lifetime and Turning Point took the late '80s sound (particularly the melodic approach pioneered by the Gorilla Biscuits) and added a softer sung vocals and the lyrical approach of DC bands like the Rites of Spring and Dag Nasty. Other bands like Earth Crisis mixed hardcore with death metal growls and slow brutal guitars. Today many bands continue to play the early '80s fast, thrashy style as well as the so-called '88 or youth crew style, while still others have taken the sound of bands like Earth Crisis farther and mixed in more metal elements such as double bass drumming. Hardcore refers to all of these styles, though metalcore is best used to identify bands like Throwdown or Converge (who don't really sound anything alike but both mix metal and hardcore). Finally, some bands like Bane, With Honor, and Comeback Kid are mixing positive youth crew style hardcore with more complex metal riffing without straying into the beatdown, double bass drumming style of metalcore. People talking about old-school hardcore should be referring to one of the hardcore sounds that developed in the '80s, regardless of when the band formed.
early '80s: Minor Threat, Government Issue, Black Flag, SSD, Jerry's Kids, Youth Brigade, Bad Brains, Agnostic Front, JFA
late '80s/'88 style: Youth of Today, Cro-Mags, Uniform Choice, Chain of Strength, Bold, Gorilla Biscuits, early Turning Point
emo-influenced hardcore: Lifetime, Falling Forward, later Turning Point
early metalcore: Earth Crisis, Strife
modern metalcore: Throwdown, Unearth, Adamantium, Converge
modern youth crew/old-school bands: Ten Yard Fight, In My Eyes, Champion, Give Up the Ghost (formerly called American Nightmare), Black Sheep Squadron, the Spark, Trial