You never know what to expect from a Zeek Sheck performance – in fact, if you attend venues like Kimo's, Club Hot, or the Stork Club, you may have seen her and not known it. If you encountered something that made you really uncomfortable and confused, sandwiched between a bunch of punk bands, it could have been her. For example, last Thursday night in the Tenderloin, Zeek Sheck showed us how to end it all.

Zeek Sheck, who moved here three years ago from Chicago, has released records on the Skin Graft label (which doubles as a publisher of comics), one of the progenitors of the mask-wearing art-core diaspora. Zeek Sheck has a real name, but like Spider-Man, she shields her identity with costumes; these have included dual styrofoam heads, face paint, and freaky unitards recalling voodoo priestesses and sand creatures.

On this night she was dressed in a corporate outfit with a paper bag over her head. Armed with a laptop, various pedals, and a keyboard, Zeek Sheck ran through a sound check that promised noise at frightening volumes (a couple of barflies were visibly disturbed by the aural assault). But instead of the kind of head-on wallop that noise acts tend to abuse, she chose to open the show with a simple set of visual aids.

The night's agenda started with Zeek Sheck reading text from her laptop about how to commit suicide using gas. Masks were provided by an assistant to facilitate helium inhalation – perhaps to allow the breather to leave this earthly coil with a falsetto that would make the angels jealous. Technical specifications, read in Zeek Sheck's mumbling monotone, followed. The assistant, also wearing a paper bag, held up what was called "Exhibit A," the type of oxygen mask that's designed to drop from an airplane's overhead compartment in the event of a sudden loss of cabin pressure.

Discussion followed regarding what size helium tank to use, differences in lung capacity, and the amount of time necessary to, as she put it, "do the job" right. On paper this sounds morbid, but as a reenactment of workplace culture and its deadening PowerPoint presentations, it was sly satire.

Then came the music. Hissy, forceful tongue baths unfurled from the laptop and were tweaked in the mixer. A member of the ensemble provided small squeals on a saxophone, and the beats congealed into a thin surface layer, while Zeek Sheck made the most of her muffled microphone. Her attack, at its most accessible moments, was aided by a lazy lyrical cadence. She seemed to be mumbling in rhythm along with the beat, using free association delivered in pidgin Japanese and English/programmer code. If – as Laurie Anderson says – language is a virus, Zeek Sheck's vocabularies and phonemes mutate in quarantined isolation, like the girl in the plastic bubble.

The entirety of the set felt improvised, and in her hands this unpredictability was a good thing. She thrives in performing right on the edge of not-knowing. When the masked freaks invited the audience to take home helium-inhaling paraphernalia, you had to wonder what the set had been leading to; the feeling that the performance was thrown together haphazardly was impossible to ignore. Still, its risky nature was what made it a success.