“It just involves moments where we both shut up for a second”: Two legends of fretless bass, one whip-smart genius shredder – here’s how the mind-blowing Testament x Pestilence fusion project Quadvium came together

The genesis of Quadvium – the extreme fusion project from fretless bass guitar visionaries Steve DiGiorgio (Testament, Death, Sadus) and Jeroen Paul Thesseling (Obscura, Pestilence) – dates back to the mid-’00s, with the two slippery rhythm-stringers excitedly talking shop after meeting at a European metal fest.

They quickly developed a bond, and over the years – whether reconnecting in their respective home bases in California’s Bay Area or the Netherlands – they started toying with the idea of forming a fretless fraternity to transform the game forevermore.

Two decades into their friendship, they’ve charted a fresh course as Quadvium. After conceptualizing the project over Zoom calls, the pair linked up in an Amsterdam rehearsal space with Pestilence drummer Yuma van Eekelen to start fleshing out new music. That’s when the bassists made a horrifying discovery: while both were virtuosic fretboard freaks of the highest order, neither were natural songwriters.

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“We suddenly realized between the three of us that nobody possessed the ability to just pull something out of thin air and make it a composition,” DiGiorgio says. “It was important to find a final member to not only have chops but the intellect to write and support our fuckin’ wacky idea of having these two fretless bass players interact.”

The musician that brought things together is Eve, a mononym’d shredder from Boston who Thesseling had been following on Instagram. He DM’d the guitarist, asking if she’d take a crack at composing for Quadvium, and Eve accepted the challenge.

At any given point, the group’s stunning seven-song debut album, Tetradōm, merges classical themes with death-metal grotesquerie and prog. Building off Eve’s foundations, DiGiorgio and Thesseling finessed the tracks with their respective aesthetic – from the former’s grit-and-gain-surged fingerings, to the latter’s crystal-toned, seven-string octave slides.

QUADVIUM - Náströnd (Official Music Video) - YouTube

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The bassists entwine for feverish, caterpillar-crawling moments of jazz-metal counterpoint (Apophis); other times they maintain a technical, yet conversational back-and-forth (Náströnd).

No matter the approach, the goal was to have “no dominant factor” in their music, this extending to how Eve also brings expressive, horse-whinnying whammy bar work to Tetradōm. In other words: Quadvium aren’t operating as a duopoly.

“Instead of making it a dualistic thing with two basses playing solos left and right, we were looking for a way to put basses in a group, functionally. In a very musical way, not to show off,” Thesseling says. His bandmate distills the ethos even more simply: “It just involves moments where we both shut up for a second.”

QUADVIUM - Apophis (Official Music Video) - YouTube

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Coincidentally, Eve had acquired a Warwick fretless bass just before Thesseling had reached out; she’s actually the one who closes the album’s smooth-fusion finale, Eidolon, with a soul-glowing set of low-end slides.

“Writing our songs inspired her to get better on bass, and within a short period of time she passed me and Jeroen’s ability like it was nothing – just commanding the instrument right out of the box,” DiGiorgio says with a laugh of his Quadvium compatriot, adding of her many talents, “Like, holy shit… Eve was indeed a total godsend to us.”

• Tetradōm is out now via Agonia.
• This article first appeared in Guitar World. Subscribe and save.