Nisennenmondai's obsession with repetition and minimalism reached almost meta levels on the releases that came after their breakthrough N: N' reworked the album's songs and included a pair of Shackleton remixes that underscored their commitment to "organic techno," while Live at Cloud Hills reaffirmed the album's precision wasn't the result of studio trickery. Just when it seemed like they might be endlessly -- and perhaps fittingly -- riffing on N, Nisennenmondai reaches another level on #N/A. Masako Takada, Yuri Zaikawa, and Sayaka Himeno find an inspired accomplice for their boundary-pushing experiments in rhythm and space, in dub mastermind Adrian Sherwood, another expert in these matters. With his help, they use the tenets of dub as creatively as their seemingly traditional guitar/bass/drums lineup. Thanks to creatively applied echo, delay and reverb, they explore new extremes of tension and starkness; in this album's world, a ricocheting drum hit is a virtuosic solo. Skeletal and full-bodied at the same time, #N/A is full of hypnotic activity. The almost unbearably tense "#1" pares Takada's guitars down to insectoid scrabbling as Himeno continues to create her own eloquent language of kick and hi-hats; later, she generates sparks on the cavernous "#4" and evokes whirring blades on the standout "#5." Nisennenmondai makes the most of the opportunity to stretch their sound on #N/A, sometimes literally: Something as simple as slowing down lends a drastically different feel on the 16-minute "#2," a masterful exercise in suspenseful interplay and dead calm atmosphere. Even when they return to more familiar territory, whether on the brief outburst "#3" or the live versions of N's "A" and "B-1" they recorded with Sherwood after making this album, it still feels like a departure -- that's how dedicated Nisennenmondai is to challenging their listeners. However they adapt, it's always on their own terms, and #N/A is some of their most radical music yet.