Tortoise opens its fourth album Standards with a blast of noise that sounds at first as though it's going to morph into "The Star-Spangled Banner"—a reasonable assumption, given the album's cover image of a distorted American flag. Instead, it remains monotone and anarchic for a full two minutes before giving way to a rhythm track and a faintly Middle Eastern organ signature. If the jumble of symbols and letters in the liner notes can be deciphered correctly, the song is called "Seneca," but easy interpretation is far from the Chicago instrumentalist collective's standard operating procedure. Standards proceeds through nine more tracks and 38 more minutes of textured percussion and heavy electronic buzz before trailing off undramatically at the end of a mellow cut titled "Speakeasy." According to insider reports, unlike Tortoise's previous two discs—where digitally recorded jam sessions were manipulated into compositions after the fact—much of Standards was previously composed (albeit loosely) and performed straight to tape, with fewer overdubs and edits. Whether the band's sound has been substantially modified is an open question; Tortoise still tends to withhold hooks and flashy solos in favor of patterns of sound that overlap at unusual points and occasionally spill into small, lyrical pools of instrumentation. When "Benway" breaks free of its obscure bent for a few choice seconds in a melodic explosion of vibes and synthesizer, the effect is uplifting. But is the joy of that brief passage intensified by the persistent restraint, or would more frequent concessions to melody make for even greater pleasure? That's another open question. Still another is this: Given that Tortoise's previous recordings have spawned a procession of remixes and re-imaginings, is Standards to be judged on its own merits, or as the raw material for music yet to come? As always, the band is poised between capturing a momentary, malleable inspiration and shaping that moment into some timeless anthem, and as always, it chooses to dither and delay, settling for a sometimes pleasant, sometimes maddening, almost always stimulating exploration of atmospherics.