When Autechre’s SIGN dropped in October 2020, its hour-long running time and comparatively consonant tones marked a major shift from the tangled sonics and mazelike dimensions of 2016’s four-hour elseq and 2018’s eight-hour NTS Sessions. But Sean Booth and Rob Brown often have a trick up their sleeves: Just two weeks later they released PLUS, featuring nine additional tracks presumably cut from the same sessions. Darker and more turbulent than its predecessor, PLUS trades SIGN’s frequently rosy blush for squalls of dissonance. Brief but potent, “DekDre Scap B” sets an ominous tone with metallic drones and arrhythmic shudders that suggest a submarine tearing apart at the seams. The tensions at the heart of Autechre’s work, as randomness pulls against dance music’s repetitive structures, have long suggested a tug-of-war between the duo and its labyrinthine software creations, and on PLUS, it’s easy to get the sense that the software is winning. “7FM ic” shuffles like a cybernetic zombie, buffeted by noxious blasts; “marhide” begins with drum sounds familiar from electro’s classic TR-808s, but the hesitant groove, nearly suffocated in a fog of white noise, transmits the opposite of electro’s kinetic energy. That’s not to say there aren’t some jams here: “X4” spins canonical IDM’s jittery rhythms into a 12-minute epic, while “TM1 open” gives acid techno a heart-racing nudge. And there are a few moments of spare, almost delicate beauty: The stately chords of “esle 0” sound like church-organ music from the 23rd century. But by and large, PLUS sounds like Autechre is giving free rein to their machines and inviting us to come along for the thrillingly unpredictable ride.