After almost 20 years and various collaborations, remixes, and bifurcations (and rhythms, resolutions and clusters), Chicago's preeminent instrumental jazz-and-dub-influenced post-Kraut (and post-rock) crew Tortoise still sound restless as ever. Look no further than "High Class Slim Came Floatin' In," the 8-minute opener to their sixth proper full-length Beacons Of Ancestorship, the first since 2004's It's All Around You (not counting ...