By Michele Romero
Updated February 05, 1999 at 05:00 AM EST

Smog is Bill Callahan, a four-track recording savant known for beautiful stripped-to-the-bone arrangements of slowed guitar chords and a halting but sturdy tenor. On his seventh release, Knock Knock, he turns extrovert, rocking out with a band, a string section, and even a children’s choir. The energy jolt serves him well, making the delicate broken spirit of his lyrics cathartic rather than depressing. B+