True Widow is nighttime chill music for metalheads: slow, drop-tuned, repetitive, reverb-heavy, and dirgey. Now three albums in, the Houston trio has firmly ensconced itself in this particular format, with little variation. It’s supremely satisfying in its simplicity and adherence to the formula. The highlights of its third and most recent album, Circumambulation, are subtle: the blistering guitar tones on “S:H:S” and “I.M.O,” the hints of poppiness on “Four Teeth” and “Numb Hand.” While change might normally seem like a good thing, in this case, evolution seems overrated. At the Great American Music Hall (859 O’Farrell St., San Francisco), opening for Chelsea Wolfe.