When Soundgarden released the masterful Superunknown in the spring of 1994, the Seattle-centric sound generally referred to as “grunge” had pretty much achieved worldwide dominance.

While the other major bands credited with flying alternative nation’s flannel flag across the globe -- Nirvana, Pearl Jam and Alice in Chains -- had already achieved platinum sales status, Soundgarden had somehow failed to break through that barrier. At least not until they took a leap into the Superunknown. Their fourth full-length album, released on March 8, 1994, vaulted vocalist/guitarist Chris Cornell, lead guitarist Kim Thayil, bassist Ben Shepherd and drummer Matt Cameron into multi-platinum, MTV-conquering superstars.

Even better, Soundgarden accomplished this feat very much on their own terms. Yes, Superunknown boasted a lot more production polish than the quartet’s humble, post-hardcore debut, 1987’s Screaming Life EP -- not to mention a less rigid and metallic-sounding mix than even its acclaimed immediate predecessor, Badmotorfinger -- but its increasingly finessed material was no less challenging or unconventional.

Instead, for all of the brighter recording tactics employed by new producer Michael Beinhorn, exemplary songs like "Let Me Drown," "My Wave" and the title track still indulged in oddball arrangements that fused bruising riffs with gnarled melodies, blazing lead guitar runs, and Cornell's elliptical lyrics. Others, like Shepherd’s Indian sitar-emulating oddity, "Half," and droning doom slogs like "Mailman," "4th of July" and "Like Suicide" simply dove off the deep end of commercial reason.

It was classic rock as seen through the eyes of Salvador Dali.

By comparison, edgy singles like the sublimely downcast "Fell on Black Days," the reverse-gear empowering "The Day I Tried to Live," and the wonderfully eccentric (yet still irresistible) "Spoonman" all managed to succeed commercially in spite of their stubborn abrasiveness — a measure of Soundgarden’s inspirational zone throughout these sessions.

Even Superunknown’s biggest hit, "Black Hole Sun," flew in the eye of convention. Soundgarden made a mockery of the “power ballad” concept by turning it inside out via haunting, impenetrable rhymes, melodies flirting with nauseous dissonance, and a positively nightmarish technicolor video filled with freakish special effects.

At the end of the day, Superunknown’s only arguable weakness was measuring in at a CD-busting 74 minutes, challenging even the staunchest supporters to absorb it all. But that didn't dissuade some 10 million listeners from picking up a copy of their own around the world. Thus, Soundgarden’s fourth album easily qualifies among the biggest-selling rock albums of the ‘90s and, perhaps most importantly still: one of the decade’s most unique and daring.

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