When Susan Duff, a retired singer and suffragist in 1920s Montana, agrees to give vocal lessons to her ex-lover's black chauffeur, the wrath of the Klan is just one of her worries. Foremost is her pupil, scarred veteran of ranch and rodeo with a voice as ''rough as a cob.'' Then there's her cattle-baron beau, a decorated vet and disgraced politician. This disparate threesome confronts not only racial animosity but their own turbulent history, buried family ties, and divided loyalties. As the narrative zigzags in time and space, veering back to the 19th century and forward to WWI France and jazz-age Harlem, Doig maintains a firm grip, aided by limber, burnished prose.