(Yeah, Doug, but I bet the little dudes didn't think it was so funny. Anyone seen that movie "Faranelli" -- I think that was the name of it. Very interesting...)
Joerg, a lot of country music or countrified folk and some blues have that little break in the voice. If I were standing right in front of you I could probably teach you in ten minutes. But the way I learned it and the way just about everyone does is just to listen to songs that have it and sit around by yourself (unless you have a very patient family or a deaf cat) and practice it. (Ever listen to Karla Bonoff? That song "Home" has some nice examples. Listen to the "Trio I" and "Trio II" CDs with Ronstadt, Parton and Harris, too.)
This is a lot like trying to explain verbally how to ride a bicycle ...