One half of the duo Caspa and Rusko, London's Caspa is one of dubstep's heavy hitters, and for good reason. One of the inventors of the signature "wobble" sound -- a low-end upheaval that recalls liquefying earth under seismic tremor -- his tracks and DJ sets apply the energy and violence of jump-up drum 'n' bass to dubstep's darker, murkier sound. Caspa got his start as a U.K. garage DJ, inspired by the likes of DJ Zinc and Oris Jay, and soon found himself playing on Rinse FM. But it was his 2004 track "Rubber Chicken" that announced his arrival as a formidable producer, paving the way for the ultra-slow, crunked-up "half-step" style that would dominate clubs. Fond of titles like "Cockney Violin" and "Big Headed Slags," Caspa and his label Sub Soldiers evince a mean-spirited, almost misanthropic vibe, turning reggae's languid cadences into hard, metallic rave-ups laced with breakbeats made for moshing.