Tortoise have always emphasized their connection to Chicago, and never more so than on The Catastrophist. Arriving six years after Beacons of Ancestorship, its roots date back to 2010, when Tortoise were commissioned to write music inspired by their hometown's jazz and improvised music scenes. Though they fleshed out those compositions for the album, the original project's sense of adventure remains. Fittingly, the title track has some of the closest ties to the album's beginnings, holding together shifts between knotty, busy electro-funk and the kind of brooding post-rock Tortoise helped define in the '90s with nimble drumming indebted to jazz. "Shake Hands with Danger" is even more audacious, nodding to the Windy City's free jazz and noise rock legacies with jabbing riffs and rhythms and chromatic percussion that sounds metallic in both senses of the word. "Gesceap"'s duel between winding synths and linear guitars feels spontaneous enough to be a rangy improvisation, while "Ox Duke" goes deep instead of wide, building on its eerily pretty vibe with meditative repetition. On each of The Catastrophist's tracks, the way Tortoise puts together post-rock's building blocks sounds as fresh as ever, with the band recombining a record store's worth of influences expertly and often playfully: The synth interlude "Gopher Island" recalls Mark Mothersbaugh's music for The Life Aquatic with Steve Zissou; "Hot Coffee" lives up to its funky title; and the closing track "At Odds with Logic" sets the album adrift on a tide of surfy guitars. Even the album's most unexpected moments feel completely natural. In Tortoise's largely instrumental body of work, tracks with singing would stand out anyway, but The Catastrophist's vocal cameos are also great in their own right. Todd Rittman of U.S. Maple and Dead Rider guests on what may be the album's riskiest song, a cover of David Essex's "Rock On" that brings a jagged edge to the original's jittery cool and proves that Tortoise can make verse-chorus-verse rock their own. Later, Yo La Tengo's Georgia Hubley takes a star turn on the gorgeous "Yonder Blue," a ghostly reinvention of '60s pop-soul that also recalls Broadcast and Julia Holter at their finest. Amidst these experiments, the band revisits fundamentals on "The Clearing Fills," a serene study in chiming guitars and electronic percussion that echoes other post-rock greats like Stereolab and Mogwai, and on "Tesseract," which, with its angular melody and tricky tempo shifts, may be the most traditionally Tortoise song here. In some ways, The Catastrophist feels like a microcosm of the band's body of work; even though they don't repeat themselves, it all comes together in some of their most immediate music to date.