In 1999, nü metal bands like Korn and Limp Bizkit were huge, often securing the top slots on MTV’s Total Request Live. While these bands and others like them reinforced misconceptions about heavy metal as just another mindless facet of pop culture, the legendary Oakland collective Neurosis released Times of Grace, an album that doubles as an argument that aggressive music can be as profound as any other style.

Neurosis recently reached its 30th anniversary. In celebration, the band embarked upon its longest U.S. tour in more than 15 years, and Relapse Records reissued Times of Grace and the accompanying Tribes of Neurot record, Grace, on September 4, 2015. Neurosis is also at work on a new album.

Some heavy bands settle into one main sound, churning out slightly altered regurgitations of the same album. But Neurosis is in a constant state of evolution. The band started in 1985 as a hyper-fast crust-punk outfit and eventually developed into a genre-defining post-metal act, using synthesizers, complex rhythmic patterns, painfully slow tempos, and transitions from delicate ether into walls of venomous distortion.

During the mid-’90s, the members of Neurosis started exploring the realm of electronic soundscapes in their sister group, Tribes of Neurot. When Neurosis began writing the follow-up to 1996’s relentlessly crushing Through Silver in Blood (also reissued by Relapse this past September), they smartly took the approach of exploring more dynamic shifts between quiet and loud instead of simply trying to write a more pulverizing record. They also decided to compose a Tribes of Neurot accompaniment, Grace, which is designed to play at the same time as Times of Grace, though both albums function as stand-alone pieces as well.

Robert Walser’s essay, “Eruptions: Heavy Metal Appropriations of Classical Virtuosity,” published in Popular Music, discusses some ways in which metal musicians have been influenced by classical composers. Walser writes, “Heavy metal guitarists, like all other innovative musicians, create new sounds by…fusing together their semiotic resources with compelling new combinations. Heavy metal musicians recognize affinities between their work and the tonal sequences of Vivaldi, the melodic imagination of Bach, the virtuosity of Liszt and Paganini.” Walser focuses on guitar heroes like Ritchie Blackmore, Randy Rhoads, and Eddie Van Halen, specifying how their playing uses characteristics of the above composers. In many ways, Neurosis also employs elements of classical music. But the guitarists that Walser discusses mostly do so via lightning-fast solos, whereas Neurosis illustrates orchestral influences by the way their albums fully envelop the listener, and also how their compositions attain meaning through epic transitions between light and dark. Playing Grace and Times of Grace at the same time only enhances these characteristics.

Neurosis recorded Times of Grace with the masterful engineer Steve Albini at Electrical Audio studios in Chicago. The band members then tracked Grace by taking turns with an ADAT recorder, passing it around to each other. They mixed the final piece at Seismic Sound studios in San Francisco. The CD insert for Grace is partly an instruction manual for playing the albums at the same time. It suggests that “synchronization times within five seconds [ahead or behind] are…nearest the ‘perfect’ ideal of the project.” Interestingly, variations in sync time alter the overall experience, making listeners active participants in the music. Although a five-second gap between play times is the recommended guideline, the album’s liner notes also say that “many interesting and unexpected results are gained through the randomness of longer discrepancies.”

Playing either album on its own is intense, but playing them at the same time will compress your psyche with despair. Times of Grace begins with “Suspended in Light,” an ominous prelude to the rest of the album. A beeping guitar effect melts into notes that slide across the aural canvas. Drummer Jason Roeder pounds a portent of war on his floor tom as these guitar sounds coalesce into a noxious haze of distortion. Grace fills in the space between these instruments with a mechanical whir, like that of an old movie projector, and eerie spoken-word vocals.

Playing Times of Grace alone, there are distinct separations between each song. But Grace is an auditory adhesive, weaving the pieces together with fluid transitions, similar to the way movements of a Beethoven symphony blend into each other. Toward the end of “Suspended in Light,” a subtle yet menacing electronic drone arises on Grace, which fuses this track with the pummeling second song on Times of Grace, “The Doorway.” The opening section of this cut pulses in a disorienting, oddly timed meter, which is highlighted by Roeder’s syncopated grooves and nimble fills. Guitarists-vocalists Steve Von Till and Scott Kelly’s sandpaper screams add fangs to this serpentine progression. The phantom ether of Grace swirls above all of this in a malevolent atmosphere.

On the third song, “Under the Surface,” Grace also functions as a looming sonic cloud, beneath which the bore of Dave Edwardson’s charging bass and Roeder’s labyrinthine drumming carves through a barren tundra of guitar and synth. When the band transitions into a monolithic half-time groove, the added layers of Grace become a physical presence rather than clearly discernible sounds, working like a plow on a Mack truck carrying a two-ton load of sludge metal.

Although this listening experience allows for some leeway in playback times, these two albums are the polar opposite of a random coupling. In an Electronic Musician article called “Tribal Connection,” Steve Von Till detailed the writing process of Grace for writer Rick Weldon. Von Till said, “The first rule was that Grace had to have the same flow, but without rock. And once we decided we wanted the two CDs to play at the same time, Grace also had to happen without rhythm. There’s no way two CDs are going to be perfectly in sync, so it had to be arrhythmic.”

The rest of the tracks on Grace and Times of Grace complement one another on several levels, and Noah Landis, Neurosis’s noise maestro (he plays keys and synth and also orchestrates samples and effects), served as an integral role in achieving that. Weldon wrote, “While working on a Tribes song, Landis would pull samples from the corresponding Neurosis song, drop them an octave, and move them around in the stereo environment.” Landis told Weldon, “Those samples are still in the right pitch, and they make reference to the Neurosis album…Even though it’s a different sound and texture, your mind hears the connection.” The instruments in a Mozart symphony dance with one another in similar ways.

The fourth track, “The Last You’ll Know,” clocks in at more than nine minutes. It comes out swinging with an abrasive, mid-paced dirge that’s peppered with Von Till’s Tom Waits–style yowls and slowly traverses into melancholy post-rock, across which bagpipe notes slither. Grace emphasizes these notes by reshaping them into ribbons of synth that inhabit the same harmonic space as John Goff’s bagpipe work on Times of Grace. The albums come together in this section to create a sense of glimpsing into a different dimension, where everything is inverted yet oddly similar.

Times of Grace also directly integrates classical music by including string and wind instruments throughout. Near the end of the album, “Away” lilts with hopelessness, a feeling communicated equally by Von Till’s broken-down clean vocals and mournful cello and violin, courtesy of Jackie Gratz and Kris Force, respectively. The final song, “The Road to Sovereignty,” starts with minimalistic acoustic guitar and drums, which become the center of gravity for a revolving mass of cornet, tuba, violin, cello, and trombone. Instead of cluttering this musical tapestry, Grace quietly lurks in an ambient background until the orchestral instruments and drums dissolve, leaving the listener with the same mechanical whir from “Suspended in Light.”

In 2002, three years after these albums were released, Leonardo Music Journal published a short essay called “Some Sadomasochistic Aspects of Musical Pleasure” in which Reinhold Friedl discusses the contemporary trend of listeners seeking out music for reasons other than “pure pleasure—pure pleasure being comparable to relaxing in a warm bathtub.” According to Friedl, challenging music creates a sadomasochistic dynamic. Because the musicians cause pain for listeners, there’s an element of sadism there; but the musicians inhabit these punishing sounds by writing and playing them, which is masochistic. (Watch any video of Neurosis playing live, and you’ll see that the performances are painful for every member of the band.) For listeners, consuming albums like Grace and Times of Grace is, through Friedl’s lens, also masochistic, since we do so willingly.

The ending piece of Times of Grace, “The Road to Sovereignty,” is beautiful; however, in order to reach this point, you have to wade through the quicksand of songs like “End of the Harvest” and “Times of Grace,” both of which are only more abrasive and intense with the added squall of Grace. Friedl posits that music is a mirror for the culture that produces it. If we judge from Neurosis and Tribes of Neurot’s compositions, our culture is defined by negativity and fleeting moments of beauty, many of which are tinged by sadness.

A large part of contemporary pop culture revolves around escapism, which often reinforces a kind of self-centered detachment. In this context, brilliant and sadomasochistic music like Times of Grace and its counterpart can better equip us to directly face the uglier aspects of society.