Here's something interesting.

A few years ago, a woman with a doctorate in choral directing came to give our church choir some tips. She told that us that some people with southern accents use 'umlauts' or front vowels. I didn't believe her. But I've been listening since then, and she's right.

Here's a link to a nice song with yodeling by Frank Ifield. (I came across it while searching for some of the singers mentioned here.) Listen when he sings 'true' and other words with a long u sound. There's a long e sound in the u's. That's an umlaut.

http://www.youtube.com/watch?v=UQAMXQosWR8&feature=related

When I learned about umlauts in German class as a fourteen-year-old, I never thought I would be hearing them in American country music.