Since ambient music discovered post-rock, less and less of it is content to remain labelled as “background music.” It’s become more forceful. It surrounds your brain rather than nesting in it. But “Precious Dive” doesn’t demand your attention so much as politely request it. Heathered Pearls has built a tiny storm of sound, starting with a trickling loop that becomes a slight monsoon near the middle, with cycles of distortion that cascade into snaps like heavy raindrops on the roof of your home. It leaves the same way it came, whispering that loop like an unassuming mantra. “Precious Dive” doesn’t need much, other than your attention. You’ll be rewarded if you grant it that.