I just read the best book on voice I have ever come across. It is "Freeing the Natural Voice" by Kristin Linklater. It was written for actors. The main thrust is getting in touch with your emotions and letting those emotions be expressed in your voice. There are many exercises to release tension. She uses visualizations with the exercises. There is a chapter on exercises for the soft palate. There is a chapter on "Why the Voice Doesn't Work". Maybe your library has the book. If not, it is currently available.
Micki Nellis