In the world of heavy experimental music there are few with as much clout as Aaron Turner. He founded the seminal record label HydraHead, fronted the post-metal goliath Isis for more than a decade, and has had his hand in so many groundbreaking side projects (Old Man Gloom, Mamiffer, Jodis, Split Cranium, to name a few) that it's hard to keep track.

After all that time, you'd think Turner would have his process down to a science. But moving from band to band, working in different ways with different people in myriad settings and configurations, he says, has kept things fresh and fun.

"I feel there's strengths and weaknesses in each way of doing things," Turner says. "That's why I choose to do so many different things. [It] helps me reassess what I do and figure out better ways of developing my personal craft."

For much of the time since Isis dissolved in 2010, Turner has busied himself with Mamiffer, an eerily beautiful (though not particularly abrasive) band that he and his wife, vocalist/pianist Faith Coloccia, started in 2007. And though he has continued to write and record with musicians of all varieties, either through sparse studio sessions or Internet file sharing, Turner seemed to have put the full-time metal life behind him. In reality, he says, he was quietly constructing Sumac in his head. The band will play Valley Bar on Monday, May 30. 

"There is a way of songwriting that couldn't be done with file trading," Turner says, "feeling that collective energy and using that as a guide."

Turner, who now lives in Washington state, had specific goals for Sumac, and was willing to wait for the right players to avail themselves.

"I'm the primary songwriter, and I just tried to find the best possible participants I could," Turner says. "The approach to this whole project has been to follow the guidelines I set within the compositional framework, sort of just the idea that a very minimalist approach was going to render the strongest result."

Turner says he set out first to find the right drummer for the band.

"I think the drums do so much to define the way a band sounds," he says. "I had been going to shows in the Seattle area for years, investigating drummers, casually examining people."

Turner says he was immediately drawn to Baptists drummer Nick Yacyshyn.

"Nick was the only person I really got excited watching play," Turner says. "He's amazing. He had the intensity and the creativity I was looking for. Sometimes [the drumming] is a thing people don't even know they're hearing. They might not notice the patterns, but it does so much to impact the character of a band."

Yacyshyn says he, too, was excited by the prospect of playing in Sumac.

"The first time we played together, there was an undeniable connection and a seemingly limitless well of ideas to explore," Yacyshyn says. "Our collective musical energy was something that needed to be pursued, and I think we both felt that right away. We both have somewhat uninhibited musical brains and are both willing to experiment until we get the results we're after. Aaron's riffs and song structures are unique and unlike others that I have heard, and doing his songs justice and exploring the musical textures and unconventional subtleties without making him change or dumb down a part so that it 'makes sense' is a priority for me."

Baptists, it turns out, is a band that doesn't do much touring, which made it easier to recruit Yacyshyn for Sumac. Getting the bass player he wanted — Brian Cook of Russian Circles — would be a little harder for Turner to pull off, despite the pair's two-decade friendship.

Cook was a member of the groundbreaking hardcore band Botch, and went on to co-found the genre-bending, post-hardcore band These Arms Are Snakes before settling into his current position in the instrumental powerhouse Russian Circles.

"Brian was the first person that came to mind when I started thinking about bass players," says Turner. "We have shared record space quite a few times."

Cook played on a number of Mamiffer recordings, Turner says, so he knew what to expect both musically and otherwise from the drummer.

"On a personal level, I knew I'd get along with him," says Turner, stressing the difference between a recording project and an active, touring band. "You spend a lot of time with people recording and it's nice to have people you like being around. We'd been talking about doing a project for a long time."

Russian Circles, however, is a long-running, successful band with a big following. It's not something Turner expected or wanted Cook to walk away from.

"Brian made it clear from the beginning Russian Circles has to be his priority," says Turner. "He's been doing it for a long time."

Still, the idea of doing a band with Turner and Yacyshyn was intriguing enough to get Cook involved, and the trio set about carving out time in their schedules to write and rehearse, in one room, as Sumac. Cook says the job of translating Turner's frameworks into songs helped draw him to the band.

"It's challenging because you have to get inside his head and figure out how he sees structure," Cook says. "These aren't your typical verse-chorus-verse songs. They're not even your typical longform, slow-build songs. It takes a lot of focus to see the patterns."

Despite the abstract nature of the process, Cook says there are advantages to writing songs with Turner's method.

"The flipside is that we're not trying to be the Beatles," Cook says. "We're not working with multiple songwriters and a myriad of instrumentation ideas. We're working with really stripped-down components and building off a pre-planned structure. That eliminates a lot of variables that could complicate the process."

That way of doing things also forced Cook, a more technical musician in his other projects, to work outside his comfort zone.

"It's very brutish and kind of ham-fisted, at least in the bass department, and that's very appealing," Cook says. "My work in Russian Circles tends to be more about nuance, texture, and dynamics. In Sumac, I'm just beating on an instrument for 45 minutes."

Cook is quick to point out that Sumac isn't a less-technical act, just a different kind of technical. In some ways, he says, it's more complex than what he's used to.

"That isn't to say there isn't a degree of sophistication to what we do," he says. "I think of the bass in Sumac being more of a percussive accent than a melodic tool. So I try to make every note serve a very deliberate rhythmic function. That winds up meaning I play a lot less, because I want to employ empty space to make each note have more impact. Considering how the band rarely veers anywhere near a straightforward four-on-the-floor beat, it also means I wind up doing a lot of counting in my head while we play. I've never counted to keep time in a band before, so that's a new one for me."

In the end, the waiting and planning paid off, and the band released The Deal last year. The record is raw and aggressive without being an onslaught of noise and distortion or a bare-bones art piece. That texture, Turner says, comes partly from experience but also from familiarity.

"Part of the intention with starting this band was to have a functional band and not a project that works in fits and starts," Turner says. "There's some chemistry coming about that you can only get in that setting. Again, part of the whole goal for me was finding people that I could feel comfortable playing with. I feel that we're working together in a real way. It maintains a very cohesive feeling throughout. That's a really good feeling, to have that kind of confidence at this early stage."