Vowel modifications are the best!
I gotta say, I did not have much faith in the DVD-format as a way of teaching song, but I can only say that I was wrong. The course is really good and worth it's money, Ken says you will grow your voice like crazy and that is exactly what I experienced. Looking back now, it seems so simple! But this is thanks to a good teacher with a definite "no bullsh*t" attitude (which I love, btw!). Warmly recommended!