A freewheeling blend of continental European folk music and the songs, tunes, and dances of Anglo and Celtic immigrants, polkabilly has enthralled American musicians and dancers since the mid-19th century. From West Virginia coal camps and east Texas farms to the Canadian prairies and America's Upper Midwest, scores of groups have wed squeezeboxes with string bands, hoe downs with hambos, and sentimental Southern balladry with comic "up north" broken-English...