Symbiotic to the core, pianist Vijay Iyer’s famed trio has logged nearly a decade as a cohesive unit, and as the title of this fourth outing suggests, their latest mode of exploration is all about rhythm. What’s immediately apparent is the level of communication that goes down between upright bassist Stephan Crump (a nimble force who sometimes recalls Cameron Brown in his bop prime) and drummer Marcus Gilmore. On the astral jazz workout “Optimism,” they take a complex triplet feel and ride its dips and turns with an astonishing blend of rigidity and freedom. The same holds true on “Little Pocket Size Demons”—a Henry Threadgill piece with a fitfully percussive theme that’s rendered even more demonic from the outset by Crump’s briefly bowed solo intro. Real progressive jazz is probably most demanding in the trio format, but these guys make it seem effortless.