MRI technology makes it possible for us to actually look at things that singers were never able to see well in the past. The video below gives some great singing samples—and you can really hear the differences if you’re paying good attention. And now, finally, you can see what’s going on inside the mouth to make the differences in the sounds.
This video is a great starting point for many discussions about singing. I wanted to mention just this one topic below, and then the video!
The video mentions the velum—the soft palate (at 1:04)—but he doesn’t say much about it. (See the still shot image above.) It’s the valve the opens/closes the nasal passages from the mouth. Unless it is open, you can’t get the “ping” or the “snarl” resonance that happens “in the mask”, as we say. The velum opens when we yawn. And there’s a certain “pre-yawn feeling” we can get good at identifying; that’s when it’s open. So for the maximum well-balanced resonance, you want to include the nasal cavities, and that’s not going to happen with the soft palate down (velum closed). So if you’re ever trying to brighten up a dark or dull/un-interesting sound you’re making, check to be sure the velum isn’t closed!
https://www.youtube.com/watch?v=J3TwTb-T044 (I can’t get the video to embed here, for some reason. So you’ll have to follow the link.)