The Scale of Vowel Sounds given above corresponds closely to the order of resonance pitch from the highest _ee_ to the lowest _oo_.
In the natural resonance of the vowels _ee_ is highest in the head, _ah_ is midway in the scale, and _oo_ is lowest in resonance.
LIP POSITION Figure 2 shows the best position of the lips to give the sound of _ee_.

Hold the under jaw without stiffness and as far from the upper teeth as is consistent with delivery of the pure sound of this vowel.
Figure 3 shows the best position of the lips to produce the vowel _oo_.
Figure 4 shows the position of the lips for the vowel sound of long _o_.

The opening of the lips should be made as round as is the letter _o_.

When preparing the lips to give the sound of _o_, the inclination is strong to drop the lower jaw; in practice, to develop action of the lips, the under jaw would better be held quite immovable.

It will be found possible to produce all of the vowel sounds without any change except in the form of the opening of the lips.