The sound of your voice, the resonance of your voice is greatly affected by how open your mouth is, and how you’re shaping vowels. You have total control over it! If you keep your mouth tight and small, your voice will sound AND FEEL tight and small. Try it out. Sing a simple “ah” in a comfortable range and hold it. Keep your mouth small for a minute and then drop it open. Listen to and feel the difference- it’s huge! Now play with the shape of your “ah”… try it wide and smiley. How does that sound and feel? Drop your jaw way, way open. What does that do? Find the shape that feels and sounds good to you and memorize it so you can make a habit of it.