what it really comes down to is reynolds picked the wrong terminology; it's not a 'continuum', it's a shockwave.
the hardcore continuum was not a recurring phenomenon but rather a single event that had resonance for a couple of decades after it happened. like any resonance it's intensity diminished the further away it got from the initial impact. it had half-lives.
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ah but you see you are making this cardinal error that so many make which is to talk about it in entirely sonic terms - as a genre, rather than a scene or subculture
it's both
the continuum-ness
is there in the sonic make-up, but gets less pronounced over time as other influences from external genres filter in
but the continuity is about much more than merely music - it's the infrastructure of pirate labels, particular record shops, dubplate cutting places, sometimes promoters or booking agencies -- it's also rituals (rewind, the role of the MC)
it's a continuity of personnel - certain DJs and MCs and producers who keep changing with each phase-shift - but also the population of people who are on the journey - some drop out, new recruits come in, but surprisingly large number of people carry on as fans of successive stages of this thing
it's also a continuity of geography - certain cities, certain parts of cities
as with any cultural formation, the start point is blurry (when does rock'n'roll start? in one sense, with Elvis and Bill Haley... in another sense with Big Mama Thornton 'Hound Dog' several years earlier - but some would trace it to the end of 1940s) and the end point is unclear, the formation starts to crumble slowly
there's definitely something proto-nuum about the bleep moment, and there are nuum-characteristics persisting in various musics right up to the present - half lives and quarter lives
and then there are musics being made now that are meta-nuum: commentaries on what is now history (a lot of post-dubstep will reactivate certain elements of jungle or whatever)
i would compare the post-dubstep producers to figures like Ry Cooder or The Band - eclectic pasticheurs who were making music that was a commentary or tribute to r'n'r (and adjacent musics) from relatively recent history - a scholarly or educated revision of music that in its own time was juvenile trash, beneath serious consideration
and then the people doing replica jungle or ardkore-retro tracks are equivalent to rockabilly revivalists like the Polecats or Stray Cats
it probably makes more sense to talk about a prime of the nuum - the shockwave and then the almost as strong secondary waves of energy
each person would necessarily have their own sense of when it became past its prime
if i was thinking about it structurally as opposed to in terms of my own taste, i would think there's a point where the internet becomes really enmeshed with how this music circulates and finds an audience, and the pirates start to fade in terms of their role as drivers of the whole thing - that seems like a crucial shift, pointing to irreversible ending of something
but i can remember a time when grime for instance had very little presence on the web at all, that seemed to go on quite deep into the 2000s. i was still relying on the kindness of such as Luka in terms of tapes mailed across the Atlantic to me in NYC.