This innovative, often comical Nashville-based quartet of ace musicians has revitalized the genre of the cowboy song. Inspired by the 1930s group the Sons of the Pioneers, the quartet includes two former Ann Arborites, Fred Labour and Doug Green. They specialize in elaborate harmonizations of cowboy folk songs, western ballads, and sentimental Hollywood versions of the real thing. Their repertoire also includes old-time fiddle pieces, some jazz numbers, virtuoso yodels, comic send-ups of western drama, and even occasional rope tricks. $35.