The energy between Harmony Tividad and Cleo Tucker of Girlpool has a motion of its own. The Los Angeles duo are sitting on an ottoman opposite me in the green room at Neumos in Seattle before their show with Jay Som and Snail Mail. They slowly slide down the sweat-slick leather surface at parallel rates (hot day), until Tucker crests the edge, almost falls off, and they both adjust their seats, laughing.

It’s kind of what Girlpool's songs sound like: sliding gently, in tandem and aware of the inevitable motion, toward a moment where they’ll both have to shift — a little startled, maybe laughing, but mostly just noticing the gravity. In their music, that moment arrives with a harmonized yell, or, as of their recently released second album, Powerplant, a wall of guitar noise. On this album they seem to be exploring how heavy the world can feel. On “123,” it's the heart-pulling drum roll before their voices escalate, in a moment of interior drama that you can imagine in the head of a wallflower at a party, realizing something about who they’re with, and knowing they can’t go back.

Girlpool play with the power of two — what harmonies can do, and what duets can reveal. Until Powerplant, Girlpool was strictly Harmony and Cleo, best friends who performed with just their voices, a guitar, a bass, and a playful ferocity. This was enough to construct a space on 2015's Before the World Was Big. Now they’ve scaled the band to explore the space. Their new approach, which includes a drummer and more complex sounds, gives their voices a break in the labor of stirring emotion. It lets them do more with their guitars, too. See the chorus in “It Gets More Blue,” where they’re able to keep the wispy inferences in their vocals as guitars fall like cement blocks of heavy realization. “I read the book / I drank the chains / I made you look,” they sigh, before they get to wail, “and I’m still here.”

If you walked into a Girlpool show pre-Powerplant and spent 10 minutes observing, you'd come away thinking vulnerable, tender, bare, and so on. Such traits being hallmarks of their shows, I wondered how their new full-band setup allowed them to maintain that particular sense of gentleness. “[We found] there were opportunities to grab onto new ideas we couldn’t actually embody before, which is a level of vulnerability, I guess,” Tividad says. “It’s announcing the thought by creating the thought, which is transparency. [Playing with a full band] opens up a vulnerability. I’m bringing a person into this work that has been ours, which is a very vulnerable space to share.”

In terms of the songs themselves, Tucker notes that “the softness, when it does show face in our set, is the contrast. That adds power.” It lets them be lighter in touch but heavier in impact, more expressive of passivity, when the music explodes in a way that isn’t entirely performed by their voices. If maturity is, in one sense, becoming more choosy with how you strain yourself, you hear that development on Powerplant. The band's more experienced at using volume for effect, which builds on their work of honing small moments rather than looking for revelations in major observations about life. “Revelations [are] such a, like…” Tucker pauses. “Every day is revelationary. ‘Revelation’ feels like it’s the end of a thought.”

“It’s a destination,” says Tividad.

“I feel like it’s all a continuous revelation,” Tucker continues. “The revelation is not having the revelation.”

“Or not expecting it,” Tividad says. “Just expecting things will continue to feel good, and then change.”

“Change is the revelation!” Tucker exclaims. “You can quote us on that!” They punctuate their Deep Thought with a burp, and then some advice not to breathe anywhere near them for about 10 seconds.

Where their individual meanderings meet, in talking and in being and in music, is the sweet spot for Tucker and Tividad. It’s the source of their ability to captivate both the adults watching from the 21-and-up balcony and the teenagers sitting cross-legged on the Neumos floor before they started. Girlpool are tender, cryptic weirdos, but in this all-ages crowd, you might wonder, who isn’t? I imagine queer kids on the floor who put “Cherry Picking” on mixes for their crushes, and girls with guitars who Google “girlpool tabs” in their bedroom, and the twentysomething couples watching from the balcony, drinks in hand, possibly being more moved by two 21-year-olds and their youthful fan base than whatever’s in their glasses. The Girlpool show is the manifestation of Cleo and Harmony’s one-of-a-kind relationship, one that can warm and welcome an entire room of strangers.

“We’re different in a lot of ways,” Tucker says. “But since we met each other, we’ve totally meshed.” Yet the pair see themselves at very different places in their lives as they begin to tour behind Powerplant. “I’ve become a much more grounded person through everything, and that’s been crazy to watch,” Tividad says. “Because I think I’ve been ... not volatile, but unpredictable in the past. I’m a lot more predictable now.”

“It’s funny,” Tucker replies, “because I feel very transient right now, like I’m observing, soaking in right now, and I’m not in control. It fluctuates. Some days I feel like we’re feeling the same thing all the time. Generally, and currently, our chapters are different.”

The name Girlpool comes from a chapter in Kurt Vonnegut’s Cat’s Cradle, but it is hard to shake the idea of the water feature it rhymes with, which is the spiraling thing that happens at the point where two powerful currents meet. Tucker and Tividad have a friendship of unique ferment, which, when talking with them, feels like a vortex of low-pitched emotional intensity. Best friends and bandmates for much of their formative years, they seem at ease in the swirling depth that their bond generates. Tucker describes it as “all of a sudden being so tight with this person that we’re doing everything together, and maybe the way they’re doing something is bruising me a little bit. It’s just like feeling different directions of the wind hitting you, and being able to be fine.” Tividad calls the process “learning passive forgiveness.”

When they’re writing together, Tividad says, “it’s not an easy thing to do. It’s not like you’re watering plants; you’re picking weeds.”

“Every time we write together it’s a breakdown,” says Tucker. “Really treacherous, but rewarding. When we play songs that we wrote together, we’re still high on the reward of finding a balance.”

Tividad agrees. “That’s a constant of our relationship — the reward of finding a balance.”

There’s the balance between the forces of themselves, and then there’s the balance among everything that a bigger experience of the world forces upon you. “Today my intention was to feel patient and forgive myself for not knowing today,” Tucker says. “I’ve been feeling like I don’t know it, really, and I’m practicing loving it, but not knowing.”

“That’s great. That’s beautiful, Cleo.”

“That’s my day.”