While technically not the first metalcore album, Cave In’s Until Your Heart Stops officiated the bond between metal and hardcore, taking it from niche crossover to full-blown genre. Released in 1998, it was arguably the first of its kind to inhale both genres and exhale them in one unique breath. Bands such as Poison the Well, Hopesfall, Misery Signals and Thrice would soon take cues from the album’s proof of concept and produce landmark metalcore records of their own. But the technical scope and dissonant creativity didn’t stop there—it appeared to assist in the development of mathcore, too. The following year, The Dillinger Escape Plan released Calculating Infinity and Botch released We Are the Romans—and in 2001, Converge released Jane Doe. Tellingly, the latter band’s involvement in the making of Until Your Heart Stops was direct and mutually beneficial. Not only was it one of the first major opportunities for Converge vocalist (and now, famed artist) Jacob Bannon to create album art, its production also deified Converge guitarist (and now, famed producer and engineer) Kurt Ballou’s profile and abilities. A four-piece by the time they entered Ballou’s God City Studio (founding vocalist Jay Frechette departed to focus on Ten Yard Fight), Cave In’s newfound leanness unearthed an even more nuanced meanness. With guitarist Stephen Brodsky stepping behind the mic came the same high-and-low throat-scraping desperation still exemplified by contemporaries to this day—with the extra aspect that Brodsky boasts a sublime singing voice as well. This elevated songs like “The End of Our Rope Is a Noose” to paralysing levels of unclassifiable mood-boarding that rival Refused’s The Shape of Punk to Come, released the same year, for historic significance. Had Cave In courted less thrash on “Terminal Deity”, more melody on “Halo of Flies” and not gleefully waylaid the relatively accessible “Bottom Feeder” with one whole minute of pure noise, they’d potentially be a household name (in select households). But a whole emergent genre of music would never have been the same. Opener “Moral Eclipse” is a post-hardcore blueprint unto itself. The eight-minute title track is the fully realised result of this blueprint, artfully towering over the middle of the album in a complex monument to every brick that built it (Brodsky even lets rip one of Tom Araya’s signature, warbling wails at 2:22). The shadow cast by Until Your Heart Stops, right up until closer “Controlled Mayhem Then Erupts” does exactly what it threatens to, remains so long it still nurtures the wet dirt of more intrepid metal’s inspiration over two decades later. This very same tendency towards exacting experimentalism would later see Cave In completely abandon the movement they helped define in favour of ethereal alt-rock that had more in common with Radiohead than anarchic arithmetic—but Until Your Heart Stops forever stands as a watershed moment in establishing an entire genre and encouraging another one with its definitive balancing act of mayhem, melody and musical osmosis.