Pianist Nik Bärtsch's Zurich quintet Ronin has released a handful of recordings, but Holon is only the second released in the United States. When Stoa was issued in 2006, it was like this startling blast of air. Was it jazz? Was it minimalist classical music? Was it acoustic techno? Bärtsch calls it "zen funk." OK, fair enough, but in actuality, while it bears traces and borrows elements from all of the aforementioned genres, Ronin is its own animal, its own sound, its own complex yet utterly accessible musical identity or, better, brand. They have toured relentlessly all over the world, and as a result, this quintet is not only well seasoned, but also it has taken the music up the ladder a couple of rungs. Stoa revealed the taut, interlocking pulses, rhythms, and grooves, all stacked atop one another with nearly mathematical precision. Given the trance-like nature of some of it, it was easy to get hypnotized and allow its subtler elements, those having to do with improvisation, however tightly scripted, into the various sections of its numbered "moduls," as Bärtsch calls his compositions, as if they are all of a piece. The Ronin personnel have not undergone changes since Stoa: Sha, bass clarinets, alto saxophone; Andi Pupato, percussion; Kaspar Rast, drums; Björn Meyer, drums. Most of these players have been with Bärtsch since the beginning and as a unit have learned to trust one another to keep frames in this music while allowing for a certain looseness that makes it more physical, more driven, and consequently more intuitive and intimate: check the breakbeats and Bärtsch's solo on Modul 41_17, where Sha moves the pulse by pitch from one sphere to the next and Bärtsch plays between the pulse and breakbeats of Rast. Basslines and percussive elements are rumbling under, pushing toward who knows what, but it's going somewhere. It actually "rocks" more than rolls, but the tension is exquisite, so much so that when Pupato introduces a cowbell and some other brighter percussion instruments in certain places, it startles the listener, like a minor shock. It is only then one realizes that the groove is mutated, shifted, turned toward another rhythmic sphere -- Meyer's carrying more notes in his groove now -- another set of pitches and contrasts and groove without the pulse seeming to change at all.