A common misconception in singing is that the mouth is a primary resonator. In reality, the mouth actually does not make a good resonator due to its overall fleshiness. For a singer to achieve a free and clear tone, the mouth must actually be “de-tuned” as a resonator. This means we should avoid directing the vibrating column of air into the mouth as a primary "feel" or thought, and we should never attempt to force the tone to be placed “well-forward.”
To understand where the voice should "live," imagine a straight line dividing your face from the back of your head. This line acts as a map for your vocal steps:
Even on a low pitch, the sensation should remain "lifted" rather than being dropped into the front and bottom area of the mouth.
When the mouth is "detuned" as a resonator, it is set free to do its primary job: articulation. The lips, teeth, and tongue are then available to shape consonants and provide the finishing touches on vowels without being hampered by the pressure of the air column.
When vocal registration is functioning properly, the air column assumes the correct height, diameter, and direction. This automatically "detunes" the mouth, giving the singer a sensation that the pitch "step" is lifted above the oral cavity. The result is a voice that sounds resonant and a diction that becomes effortless and clear.
By moving the focus of resonance away from the fleshy parts of the mouth and toward the stable "steps" of the pharynx and palate, you unlock your voice's true potential. Stop trying to "place" the sound in the mouth. Instead, focus on the lifted coordination of your registration and let your mouth do what it does best—tell the story.