Music historians on the trail of Kentucky mountain music might think that San Francisco would be the last place to look for any kind of old-time sounds. The city by the bay is about as far from Appalachia as you can get, and equally far from the concept of bluegrass. Yet San Francisco is exactly where some of today's finest old-time and bluegrass music is being played. Thanks to the Crooked Jades, the city is also a repository of the genre's history. Jeff Kazor, the band's founder and leader, has amassed an enormous catalogue of roots music culled from America's heartland. The...