Nobody could have predicted the flutes. Sewn to the Sky, Bill Callahan’s debut album under the Smog moniker in 1990, was a haphazard collection of home-recorded half-songs featuring barely-there vocals and copious noise. But Callahan’s latest, Dream River, is so clean, so mellow, so full of flutes, that it’s hard to imagine him being anything but the singular, fully formed artist he is now. His baritone voice is one of the most powerful deadpan statements in rock, and his lyrics tread a strange darkness even as his music has turned toward the light. And, man, those flutes.