The Unstable Molecule

Chicago post-rock could sometimes seem a little buttoned-up, but Isotope 217 found Tortoise members Dan Bitney, Jeff Parker and John Herndon letting loose alongside Chicago Underground cornetist Rob Mazurek and other local associates. “Phonometrics” digs into a wiry James Brown–esque funk groove, while “Beneath the Undertow” builds a smooth, danceable jam upon a sinuous vamp by bassist Matt Lux. “La Jeteé,” a showcase for the softly expressive trombone stylings of Sara P. Smith, quiets things to a dubby murmur, with closer “Audio Boxing” dialing the beat back up to a loungey simmer. A record like this now seems emblematic of a scene that had so much creativity to spare that its members were constantly spiraling out into various satellite projects, with each release feeling like a snapshot of a larger ongoing story.