Autechre albums are like language immersion programs: At first they don’t make sense, but listen close and familiar shapes emerge. Not that SIGN is accessible per se: We’re still talking about something closer to computer programming than what most people would consider music. But for a group that can be almost mythically forbidding (2016’s four-hour-long—and 12-hours-dense—elseq), SIGN is almost pop. Thirty years in and the UK production duo’s roots still show: Hip-hop on “M4 Lema,” house on “psin AM,” far-out synth soundtracks on “F7” and “Metaz form8.” But it all remains deconstructed and once removed. Most music depends on memories of something you’ve heard before. With Autechre, you can feel your brain stretch as you listen. Normally they sound like they’re pushing forward or settling in. With SIGN, it’s both.