Reputedly originating hundreds of years ago when a lonely Swiss shepherd sang across a mountain to another lederhosen-clad soul, the ancient art of yodeling has achieved a unique place in folk music. Characterized by frequent vocal flips between natural and falsetto voices -- or chest and head voices -- yodeling is an art form that can make for difficult listening. Legend has it that American country music was actually born when Jimmie Rodgers heard a travelling troupe of Swiss yodelers and incorporated the sound into his songs. To that end, there is no doubt that Rodgers introduced the vocal technique into popular music, and that his yodeling work inspired generations of folk and country artists, including Bill Monroe, Gene Autry, and Roy Rogers. Current interpreters of the genre include Gary McMahon and David Bradley in North America, and the twin duo the Topp Twins in New Zealand.