The way one uses the various parts of the larynx and the surrounding areas, such as the pharynx and the tongue in order to produce the sound determins the quality of the sound.
Several legendary US voice teachers have researched the functional use of the larynx and the muscles surrounding it. These researches offer directions in how to develop the voice from an anatomical and scientific point of view.
These teachers have created simple tools to address complex problems.
Globally, the singer has to be able to maintain a stable larynx and an easy yet precise adduction of the vocal cords throughout his or her range. This way of using the voice is protecting the voice from potential harm.
The goal is to eliminate all that is artificial in the sound, any compensation, in order to free the voice of the student as it is, in its uniquness and then to protect it, reinforce it and let it grow in range, power and endurance.
This is done by discovering and assessing the non optimal habits that the student has. These poor habits can happen in the larynx, in the pharynx, in the tongue, in the jaw, in the cervical vertebrae and many other of the numerous players that take part into that coordination.
Then one educates the voice to respond in a balanced and optimal way. Once that is happening, one develops a variety of color, volume and sounds to suit the desired musical genre that the student is pursuing.
The tools used for this are sounds and movements using vowel acoustics, consonants properties, and unfinished sounds depending on the needs of the student. Also, one uses refined mobility exercises in order to counteract accessory tension.
I have been trained in the USA with various specialists researching this field of work. I wish to thank Spencer Welch, David Jones and Lynn Martin for their influence and their inspiration.