A prominent corpse of the buried-in-six-months horror-rap genre, New York’s pseudonymous Flatlinerz — Redrum, Tempest and Gravedigger — make an inner-city joke of ghoulish violence in flamboyant hip-hop variations on Chiller Theater themes: “Graveyard Nightmare,” “Good Day to Die,” “Rivaz of Red,” “Takin’ Em Underground.” Unrelated to any high-stakes fiction, “Satanic Verses” rhapsodizes about decapitation, spirits rising from the dead, burning flesh and “bodies entwined, being hung by barbed wire.” As an innocuous antidote to the realistic brutality of gangsta rap, Flatlinerz’ thick old-school beats, trivial skits and theatrical delivery are entertaining enough but, like any novelty exercise, scarcely encourages repeated listening.