I bought Cathy F and Marcy M's learn-to-yodel tape, some years ago. I learned to do at least a rudimentary yodel (More practice would have helped me though!) But they are very good teachers.

PoppaGator, a lot of the tameness you mentioned is a direct result of the invention of radio and phonograph! Source singers often have a very personal, strong mode of expression, and they aren't trying to hit every note exactly on pitch and in time. It makes for a unique, fascinating listening experience but of course if a modern performer recorded music that sounded like that, they would come in for a lot of criticism and would lose a lot of sales.

Dwight Diller is one performer who doesn't bow to the need to be "correct" in his singing and playing. I love his feisty attitude. On the cover of his "O Death!" CD, there is this notice: "CAUTION: Squeaky fiddle contained herein. Has caused a grinding down of Molars in many listeners. In a few celebrated rare cases, listeners have been known to become addicted. Be forewarned!" And in the liner notes of his "Dwight Diller: Harvest" CD he wrote: "All tunings are relative: you will have to figure out the pitch. I don't know how I tuned for many of the songs. I just pitched them to my voice and applied an appropriate tuning."

I suspect that often, the more an artists tries to avoid flaws, or anything that could be criticized, in their performance, the more they water it down.