The term "heavy metal" -- attributed to William S. Burroughs and echoed in Steppenwolf's "Born to Be Wild" -- initially described excruciatingly loud late '60s acid-boogie bands such as Blue Cheer. By the turn of the '70s, British artists led by Black Sabbath were de-emphasizing rock's blues element and often reveling in the occult, while figuring out how to make feedback, distortion, riffs and rhythm feel heavier still. As the '80s began, New Wave of British Heavy Metal crews such as Iron Maiden and Judas Priest had begun divorcing the genre from so-called Hard Rock entirely, giving metal its own language and dress code. The '80s saw thrash speed tempos up into unprecedented aggressiveness even as the hair metal bands monopolizing MTV turned things poppier. Eventually, most '80s glam bands were excommunicated from metal consideration and '70s pioneers were rebranded "proto-metal" as the genre grew ever more extreme, subdividing into nasty substyles such death metal, black metal and grindcore. More recently, stoner, doom and power metal have harked back to metal's earlier eras, while more commercially minded rapcore and metalcore dominated radio and sales charts.