By age thirty-nine, Blair Kilpatrick had settled into life as a practicing psychologist, wife, and mother. Then a chance encounter in New Orleans turned her world upside down. She returned home to Chicago with unlikely new passions for Cajun music and its defining instrument, the accordion. Captivated by recurring dreams of playing the Cajun accordion, she set out to master it. Yet she was not a musician, was too self-conscious to dance, and didn't even sing in the shower.

Kilpatrick's obsession took her from Chicago's Cajun dance scene to a folk music camp in West Virginia, back and...