Smog has become (Smog) for its ninth album, for reasons known only to bandleader Bill Callahan. The staunchly independent minimalist divides his loyalties between openness and obscurantism, so adding parentheses around the name of his deep, dark, low-fidelity folk project is no more eccentric than his obsessively recording mellow, Velvet Underground-y drones wrapped in swirling strings, dyspeptic guitar noise, and fractured poetry. It's no odder than spending a decade dispatching that output on limited-edition cassettes, hard-to-find singles and EPs, and full-length records which line up like entries in a diary, varying only slightly in mood and in Callahan's generosity with his hooks. Rain On Lens' mood is intensely cloudy, its melodies circular and hypnotic. Defying hummability, Callahan intones flatly and nasally as he and his band shoot repetitive chords into an echo chamber. The virtual impenetrability of the music is tempered by his lyrics' wit and insight. Whether he's imparting hard-learned advice in "Keep Some Steady Friends Around" and "Live As If Someone Is Always Watching You," or defining himself in lines like "I took your party invitation list / and wrote 'enemies' across the top of it" (in "Short Drive") or "I'm a bit like the peephole / that falls in love with all the eyes" (in "Song"), Callahan embodies the indie-rock ideal. His music is idiosyncratic and personal, the rock 'n' roll equivalent of a self-published pamphlet. Whatever the typography, (Smog)'s Rain On Lens remains essential listening for devotees of the rock 'n' roll underground, supporters of assured self-expression, and those captivated by the monochromatic.