One of the core intentions of my personal vocal training is to generate the maximum amount of rich harmonic, resonant sound with the least amount of effort. This is what makes the voice sound beautiful and also what gives us our “signature sound” that makes our voice easily identifiable from other voices.
There exists vocal exercises we can do that first help us find our optimal coordination to produce our best harmonics. We do this first within our normal speaking range before we then take it through a larger portion of our range. What we are trying to do is to slightly move our lips, jaw, tongue, posture, muscle activity, larynx and so on while simultaneous finding where we get the most resonant buzz in our face and head. This buzz tells as that there’s a lot of rich harmonic content in our sound.
The subject of generating maximum resonance with minimal effort first came from speech therapy. It’s part of helping people speak properly and at length without tiring or hurting themselves. It was later discovered that this therapy did wonders for actors and voice actors. More recently it’s being applied to people learning how to sing better. Have a listen. It’s working wonders with my own singing and vocal training.