What's the biggest difference between most amateur singers and the pros? Professionals always have their mouths OPEN! Missionaries always hear the mantra "Open your mouth" when it comes to finding people to teach, but the same applies to voice students as well.
When people are insecure, the number one thing that happens is that they tend to limit the movement of their lips and keep them more closed than opened. Failure to part your lips sufficiently when singing holds back the majority of the sound and ruins the tone. It's not just the lips, though. Even if your lips are wide open you can have the rest of your mouth fairly closed off and the same thing will happen, only now you've added unneeded tension. Here's a small checklist to help you see if your mouth is open wide enough while you sing.
- Two-finger test - Take your index and middle fingers, hold them close together and insert them vertically between your front teeth. This is approximately the space you want in the front when you sing. It doesn't need to always be so tall, but it's better to air on the side of taller than not tall enough.
- Space between molars - Place your thumb and index fingers on your cheeks and lightly press in until you can feel them pushing your back molars apart. Your molars need to have space between them to release the sound from the back of your mouth, create a "megaphone" for proper tone in the space and help lift your soft palette. Don't press too hard, just enough to feel the space!
- Release the jaw - Your jaw should feel released while singing. Let it drop open and remain there while you sing. Don't force it too much as that will add tension which is what we're trying to remove. Ideally you should be able to move your lower jaw around with your hand.
Again, these are very simple suggestions, but I frequently need to remind students to move their lips out of the way so they can get good volume and improve their tone quality. If this is something you struggle with, break that habit now! You'll find making sound a lot easier, too!