Not to slight other dubstep-rooted labels productive from 2005 through 2009 — Tectonic, Deep Medi, Hessle Audio — but this half-new/half-retrospective set supplies all the evidence necessary in determining the form’s supreme source. Released to acknowledge the fifth anniversary of Kode9′s Hyperdub, these two discs, assembled in the wake of 30-plus 12″ releases and three albums, should be the starting point for anyone late to the party. There is a slight catch, though: only a fraction of the contents is truly dubstep. In short, dubstep extends and mutates dub, drum’n'bass, U.K. garage, and grime in various permutations. It’s merely a foundation for the majority of these producers, whose releases have inspired a flurry of neologisms, like wonky and even post-dubstep; each one has been met with some stiff resistance. Regardless, there is no refuting the significant disparity between Burial’s grayscale “South London Boroughs” and 2000F & J Kamata’s vibrant “You Don’t Know What Love Is,” a pair of disc-two tracks released, respectively, in 2005 and 2009. The former’s sub-bass and sweeping-scythe percussion takes rhythmic tension to the brink of oppressiveness, while the latter’s booming bass and wriggling synths spawn synthetic funk at its most voluptuous. That the first disc contains the new material speaks to the label’s desire to continue pushing. It does not quite surpass the second disc of past highlights, yet it’s nothing short of generous. A handful of comrades who hadn’t previously appeared on the label, like Flying Lotus and Martyn, make appearances; perhaps unsurprisingly, it’s the Hyperdub artists who deliver the most moving tracks. King Midas Sound’s “Meltdown” is psych ward lovers rock. On “Time Patrol,” Kode9 places crisp, tightly coiled percussive friction and jabbing strings beneath the Space Ape and Cha Cha’s urgently whispered threats/come-ons. Ikonika’s “Sahara Michael,” enhanced with sub bass and swarming strings, is one of the most complex productions, stunningly layered with drums that switch between a swaying lurch and a stomp as acidic bleeps flutter and gurgle. The second disc features most of the label’s essentials, including Darkstar’s “Need You,” Joker’s “Digidesign,” Samiyam’s “Return,” and the Rustie mix of Zomby’s “Spliff Dub,” all of which are unique and equally representative of Hyperdub. – Andy Kellman