The Underflow take their name from the Greek record store where guitarist David Grubbs, cornetist Rob Mazurek, and saxophonist Mats Gustafsson played their first trio gig in May 2019. But the connections joining the three musicians were forged in the 1990s, when Grubbs and Mazurek were associated with Chicago’s postrock scene and the Sweden-born Gustafsson played here so often that he was considered an honorary Chicagoan. Nowadays they’ve scattered across two continents (Brooklyn, New York; Marfa, Texas; and Nickelsdorf, Austria), and it takes a European tour to get them on the same stage at the same time. But the breadth of their combined stylistic and instrumental resources is even greater than it was back in the day. Grubbs contributes poetic verses and versatile electric-guitar playing; both Gustafsson and Mazurek have added rough, nonvirtuoso electronics to their respective tool kits of woodwinds and brass. Perhaps the biggest challenge they face is figuring out how best to combine everything they bring together in this group: carefully crafted songs, wordless cries, high-voltage noise, breathy exhortations, lyrical melodies. On their new second release, Instant Opaque Evening, their solution is to use the improvised negotiation of relationships among players and elements as a source of dramatic tension. At any given moment, one musician has another’s back while the third proposes a contrasting approach. In an instant, alliances might shift or someone might drop out altogether. Playing out in album-side-length segments, the music evokes the uncertainty of court intrigue and the multifaceted bombardment of a kaleidoscope.