Cathy Fink and Marcy Marxer have recorded a kids album which included a yodelling lesson where they show you how to uses the sounds ah ee ah ee
and then sing notes where ah is low and ee is higher...the jaw moves down and up as the notes do...it is fun...i think the song is about a grandmother who slides down a stair railing...or a mountain!
http://www.cathymarcy.com/ they also do trick roping
as does Sourdough Slim http://www.sourdoughslim.com/
you can hear him yodel his way into your heart here: http://www.outwestnewspaper.com/sourdough.html. He often is accompanied by the Saddle Pals when he performs. They are a hoot and would ya look at that bass viol of prairie flower's it's a beaut!