Each of sound artist Kozo Inada's prior releases had been titled similarly, beginning with a [ ] and working forward alphabetically. For the sixth in the series, he teamed up with Philip Samartzis and produced an extremely lovely single piece, a work that simultaneously maintains a devotion to a certain sound world while still making surprising deviations within it. It's a live improvisation, the two musicians using a wide range of found sounds, field recordings, and electronics, though all possess a certain rustling softness, an airy, billowing quality. As the piece looms out from the quiet, one hears what seems to be a buffeting wind alongside a crackling fire. Behind these, a slightly more mechanical sound gradually emerges, that of a thrumming turbine, perhaps. Every few minutes, just when you think things are going to settle into an attractive stasis, the sound shifts, sometimes just a bit as if a prism had been only barely tilted, but it's as if an unseen door has suddenly been opened, offering views into areas you didn't expect to see. There are always at least three or four sonic layers in action at any given point, though picking them out requires some degree of aural dexterity. Some of the strands have, in this context, an unusually tonal aspect, a little bit reminiscent of early Fripp & Eno, though they're mixed deeply enough into the roiling clouds of rumbles and static so as not to draw unwanted attention. At less than 36 minutes, f [ ] is of absolutely perfect length; it ends just at the cusp of wanting more and having had enough. It's a rich, strong and endlessly fascinating work. Recommended.