@Wikipedia : Yodeling (or yodelling, jodeling) is a form of singing that involves singing an extended note which rapidly and repeatedly changes in pitch from the vocal or chest register (or "chest voice") to the falsetto/head register; making a high-low-high-low sound. This vocal technique is used in many cultures throughout the world.

@Yodel Course : It was 1978 when I first heard The Yodel King (Der Jodlerkönig) Franzl Lang. I was visiting my relatives in Munich, Germany, when I heard a sound I had not heard before. The music made me smile and reinforced my love for the Alps. Most of Franzl Lang's music speaks of his love of Bavaria and the mountains.

@Country Music Hall of Fame and Museum : : Described by Merle Haggard as “the most unique thing that ever happened to country music,” William Orville “Lefty” Frizzell was certainly one of the most influential performers in country music history. A supreme vocal stylist, he introduced an intimate, vowel-bending style of singing

@Karin's Adventures : This song is the reason why I wanted to learn how to yodel.*Oesch's die Dritten* won a yodeling contest in Switzerland with that KuKu-Jodler. After teaching myself the basics of alpine and cowboy style yodeling, singing along with a couple of CDs, in my car on the way to work and back, I finally feel good enough to take on the song that got me started.

@Vienna Online : On a nice warm day, step outside and stay close to your front door (for safety reasons). Yell at your neighbor across the street (or the field, the lake, etc. minimum distance: 50 feet). Words like: HEY, WHY, GO work best. Duck and rush back inside, DON'T approach. Lock the door, if applicable.

@bart plantenga : In the 1930s Bob Wills posed the metaphysical question "will there be yodeling in heaven" for several reasons. If yes, then heaven'll be a rollicking joint and maybe he could front the house band; God being the manager and all. Yodeling, after all -- especially the Tyrolean lederhosen version -- is within easy earshot of biergarten oompah music -- jolly, mindless escapism -- hoist another stein

@Google Books : : Yodel-Ay-Ee-Oooo is the first book to address the question: How did a centuries-old, Swiss mountain tradition make its way into American country music? Along the way, the reader discovers that yodeling is not just a Swiss thing--everyone from Central African pygmies, Nashville hunks-in-hats, avant-garde tonsil-twisters like Meredith Monk, hiphop stars De La Soul, and pop stars like Jewel have been known to kick back and release a yodeling refrain

@swissinfo : In Alpine regions, such as the Muotatal in Canton Schwyz, the Appenzellerland and the Austrian district of Scheibbs, one to five-voice yodels without words can be heard. The Muotatal Jüüzli has two to three voices.

to be continued… probably