What is hardcore music? As Explained By Tombston3...

  "Hardcore is the style that began in the early 80s, often applied to
   bands such as Black Flag, Minor Threat, Sick of It All, Bad Brains,
   Rollins Band, Fugazi, etc.--sort of "2nd wave" punk bands.  They were
   sloppy punk bands that played with more intensity and heaviness than
   earlier ones like the Sex Pistols, The Clash, etc.  Today's hardcore
   bands are tighter and much heavier, and can be divided into two general
   types (usually called East Coast or West Coast, for where the band is,
   but it's not always consistent).  The first type are smoother, with
   heavy grooves that flow, with a vocalist that sings (or at least tries
   to) or shouts.  The second type is heavier, with tight, stop-and-go
   rhythms and harsh vocals that are a cross between shouts and low
   screams."

   "This is what hardcore means: Energy, Positive attitude,
   Rebellion, Independance, Separating from trends, Not following the
   masses, Hard-core = hard music"

   "D.O.A. popularized the term hardcore as applied to punk rock music
   with the release of Hardcore '81, a pivotal record from the early
   west coast hardcore punk scene.

   "Hardcore was (and is) uncompromising punk attitude combined with
   social activism. Sort of "punk with a message", but not to be confused
   with "straight edge" or "PC" movements, later variations of hardcore.
   West coast hardcore was completely different from the "fashionable"
   punk rock of art school students and posers - in the early days of
   punk there was a huge difference between the English-style punks
   with their fashionably torn and safety-pinned look, and the hardcore
   'street' punk who just didn't give a fuck about their appearance.

   "It's an intelligent movement characterized by a deep anger at the
   status quo. It is not surprising that it began on the U.S.west coast,
   where radicalism and rebellion has deep roots...  schools don't tell
   you much about the labour riots of the 20's or other examples of
   North American civil disobedience... Uncompromising hardcore shocked
   the complacent hippie mentality, needless to say.

   "Hardcore will never die where individualistic thought can survive -
   which of course means it has been constantly oppressed by the vacuous
   media of North America. The current popularization of 'punk' is more
   concerned with style than substance, rather a new fashionable trend
   for the pop machine.

   "Hardcore survives in bands like Fugazi, NoMeansNo, The Ex, and
   D.O.A. - hopefully with the current popularity of punk rock more kids
   will discover that the world ain't exactly a great place, and work for
   positive change despite the many evil forces in this world. And that is
   the best definition of hardcore I can imagine." [11]

  "The Germs (April 77) , Black Flag (June 77), The Misfits (first show -
   April 77), Chain Gang, The Pagans (mid-77), Canada's The Diodes (first
   lp June 77) and The Viletones (recorded Jan 1978) were already under
   the 'hardcore' banner in 1977.

   By 1976, bands like Patti Smith,
   Richard Hell and the Voidoids, and many that were playing at CBGB's
   were called punk, and I think that the (mostly) West Coast bands that
   you cite were the hardcore 'babies' of those groups.

   "without a doubt BLack Flag was the first HC band...anyone who says
   otherswise is a fool. People forget that early HC has its roots in punk
   everyone thinks that the newschool sound is what hardcore is
   about.....plus theres more to being a HC band than just the sound."

What's the difference between old school and new school hardcore bands?

   The basic musical difference is that old school is punk and new school
   is metal.

   "it's actually really simple. new school is kinda like slayer, only
   the 'kids' pretend it has something to do with hardcore. i see it as
   cheap metal.  old school (THE ONLY SCHOOL!) on the other hand is
   precisely the other way around: fast and positive."

   "Actually, "old school" depends on how old you are. If YOT is old
   school, then you need to reach back a little further into the Teen
   Idles/Minor Threat days. And that wasn't always positive. The big
   difference for me is that new school is a lot more exclusionary, a
   lot less fun, and has bigger pants."