When Mitski performed last night at the Triple Rock, she mostly stood stock still at a stage-left mic surrounded by monitors, plucking a bass and keening into her vocal mic. Meanwhile, guitarist Patrick Hyland and drummer Casey Weissbuch whipped up furious storms of sound, storms that Mitski herself seemed to be both summoning and weathering.

Playing to an easily sold-out house of rapturous acolytes, just off an appearance at the Pitchfork Music Festival, Mitski is one of the most rapidly-rising performers in rock. Though she hasn't had a commercial breakthrough, she has buzz to burn, with boundless acclaim from tastemakers at Pitchfork, NPR, and even Rolling Stone — which calls her "indie rock's brightest star."

Critics work themselves into fits trying to explain just what it is that makes the 26-year-old singer-songwriter so compelling, but their efforts to do so tend to center on Mitski's mix of anthemic accessibility and elusive complexity. A Mitski song seems to change every time you hear it, in part because her genius doesn't follow any particular set of established rules.

She squalls, but she's not a guitar god — in fact, during a few solo songs last night, she slid a finger up and down the neck of an open-tuned ax, a la Richie Havens. Her voice is haunting, but she has neither the polish of an Adele or the shambling roughness of her grungier peers. Some of her songs rise to big choruses, but they never sound calculated...it's as though she just gets to a point where a giant hook is the only way she can really communicate just what she's trying to get across.

What is she trying to get across? Like so much of the best art, it's intensely subjective but also universal. Her most-heard and most-discussed song from last year's Puberty 2 is the single "Your Best American Girl," which has been compared to Weezer for its fuzz-drenched sing-along-ability, but which has a meaning inflected by Mitski's Japanese-American background and her constantly self-reflective orientation. She's an American girl — is she the girl she wants to be? Is she the girl you want her to be? The song is simultaneously declarative and inquisitive.

Although Mitski has four albums — she got her start while still a college student, at SUNY Purchase — last night's set ran a brisk 45 minutes, spotlighting material from Puberty 2 and 2014's Bury Me at Makeout Creek. There wasn't a lot of stage banter, and Mitski announced her one-song encore by walking back onstage and chirpily declaring, "Encore!" Explaining that she was going to do a cover of Personal Best's "This Is What We Look Like," she said, "I hope you go on Bandcamp later and check it out."

The set progression was as idiosyncratic as one of her songs, playing favorites "Happy" and "Townie" early on, then hitting "American Girl" mid-set. The show's climax came just before the solo interlude that closed the set, with Mitski rising to a scream and then briefly cupping the mic in her mouth during "Drunk Walk Home."

Mitski's music is redolent of '60s pop, but filtered through so many prisms that you stop expecting any of her songs to behave like a vintage single might. The Kate Bush and neo-folk (Suzanne Vega, Tori Amos) influences are easy to pick up on because of her gender, but there's also a certain Lou Reed spirit to her songs: she'll bend pop conventions to her meaning, rather than finding meanings that fit conventions. It's an inspiring body of work, and, like her audience, it's continuing to grow.

Just before leaving the stage, Mitski looked up and smiled. "I'm going to miss you when I leave," she said. The crowd made clear that the feeling was mutual.

Openers were Half Waif, a Brooklyn artist who Mitski's been touring with; and local rockers Kitten Forever, who pounded out a trademark set of high-octane rockers but couldn't inspire much dancing. In part that was because the house was so tightly packed, and in part it was because everyone was already in the Mitski zone: ready to close their eyes and feel some really loud feelings.

Half Waif

Kitten Forever

Mitski