The idea that progressive metal is nothing more than prog rock fused with heavy metal may be frequently invoked, yet it fails to capture the movement’s fractured evolution. Certainly, it’s accurate in regard to mid-’80s pioneers Dream Theater, Queensrÿche and Fates Warning. Having grown up worshipping Yes and Rush just as intensely as they did Judas Priest and Deep Purple, these American bands explicitly marry the multipart arrangements and brainy concepts of the former with the latter’s hammering riffage and galloping rhythms. By the ’90s, newer practitioners had distanced themselves from this approach. Tool, while inspired by King Crimson, are so dark and eccentric as to be more of an alt-metal entity. As for Sweden’s Meshuggah, they compose complex epics, but they come buried under extreme metal’s monstrous chug and growling vocals. These ruptures have only multiplied in the 21st century, with progressive metal breaking off into death metal, doom, sludge and metalcore.