Vowel modification is simply: changing a vowel sound to make it easier to sing AND improve the tone quality. Why would we need to change vowels, though? Aren’t they all basically the same? No! Each vowel is the result of a slightly different shape in your vocal tract (the pathway from your larynx to your lips). Different mouth posture, tongue placement and lip closure make up the difference between an EE sound and an OO sound, for example. It’s getting a little sciencey, but I promise it’ll make sense!