In ascending the scale it is well to open the throat a little wider as you ascend.

The delivery will be much easier, and the tone produced will be much better.

At the highest pitch of the voice the mouth should open to its full width.

At the same time care must be taken _not_ to draw the corners of the mouth back, as in smiling, because this lessens the resonance of the tone and gives it a flat sound.
The under jaw must have considerable latitude of motion in pronunciation, but by all means avoid chewing of the words and cutting off words by closing the jaw instead of finishing them by the use of the proper articulating organs, which are the tongue and lips.
THE SOFT PALATE Writers on the voice have almost universally claimed that the principal office of the soft palate is to shut off the nasal and head cavities from the throat, and to force the column of vibrations out through the mouth, thus allowing none, or at most a very small part, to pass into the nasal passages.
This contention implies that the vibrations are imparted to the upper cavities, if at all, through the walls of the palate itself, and not through an opening behind the palate.

This is entirely at variance with the facts as verified by my own experience and observation and the observation of others who are expert specialists.