Whenever we produce a vowel sound, our voice muscles are immediately flexed into action. The particular vowel that is produced; the pitch on which it is produced; the volume at which it is produced; the speed at which the vowel may move through our range; the areas in our range (i.e., low, medium, high) where the vowel travels; and the intensity level of the emotion that is expressed—all determine how, and to what extent, the voice muscles are flexed. In my work, I have found five particular vowel sounds that flex the vocal muscles to an exceptional degree. I call these sounds “voice building vowels”; they are: