Perma-frowned doomsayers Mastodon are back with yetanother friendly reminder that someday everyone will die. This time, it comesin the guise of seventh album Emperor of Sand, a lofty concept piece about a manwandering a desert with a curse over his head set to swirling, frenetic guitarsand gut-rumbling drums. “Don’t waste your time/If it’s the last thingthat you do,” goes the chorus to Emperor’s boogie-metal “PreciousStones,” and the band largely took that advice to heart. The LP istheir most ambitious outing since 2011’s proggy Crack the Skye –following two relatively pared-down LPs – and at its best (the radio-readypop-rocker “Show Yourself,” the triumphal outro of “Ancient Kingdom,”the Zappa-inspired synthesizer-and-bells duet midway through “Clandestiny”)it’s a glorious metal miasma. At its worst (guitarist-singer Brent Hinds’mumbly, off-key acoustic intro to “Jaguar God,” the noodle-y “Steambreather”),it’s a potent reminder that, yes, indeed, time is precious. Mostly, they find amiddle ground that pays homage to the burly heft of Mastodon past and the headyrock they’ve always aspired to make.