The basic principles of vocal function in The LoVetri Method, Somatic Voicework™ are very simple. They are: isolation, development and combination of chest and head registers to create a balanced mix, undistorted vowels, and strong, aligned posture which facilitates deep and easy inhalation and exhalation. If you learned and understood only this about vocal production, and you applied these principles to a wide range of pitches and volumes, and added consonants, you wouldn’t need anything else to become a good vocal technician.
If you do not understand register function as an auditory phenomenon, and you do not understand that this is a vocal fold behavior as well, you can waste a lot of time on “resonance” (something you can’t control until you have a good deal of skill and power), and you can confuse vocal quality with vowel sound quality (a very bad mistake) which will make you spin your heels. If you believe that everything comes from the breathing, then you can waste a lot of time, years or maybe even decades, developing your ability to breath, but if you do not also work on your sound, all you will get from doing this is to be a really excellent breather. I have some of those folks show up in my studio. One man had worked on breathing for 12 years with his previous teacher and had made little progress. He got better working with me in about 4 sessions by strengthening his chest register, something he had never heard of.
If you have been taught that everything is “placement” and “breath support” and that breathing has something to do with inhaling into the diaphragm, (and who hasn’t been taught those things?) you can spend much much too long trying to get a person’s sound to improve, develop, grow, adjust or change to no avail.
If you can get a good strong undistorted unmanipulated free open /a/ (as in Father) on a low note at a loud vowel, you can assume that you have a healthy chest register response. If you can get a clear, light, easy undistorted /u/ (true) on a high pitch at a moderate to loud volume, you can assume that you have access to a healthy head register function (doesn’t mean you can sing a whole song there, however). If you can sing an /e/ or an /ae/ on a middle pitch at moderate volume, you probably have some kind of balance or mix. Probably is the operating word.
You have to know what kind of sound is good in order to get it. You have to know what you want before you open your mouth and you have to know that you are going to get that sound before you try to make it. Being able to do that, on demand, every time, is having “secure vocal technique”. If you do not know what “good” sounds like, especially in yourself, you have to learn. If you do not know what comfortable is, you have to learn that too. If you do not have control over all the dimensions of your voice (pitch, vowel, volume, consonants, duration, pressure (volume) and vibrato (some/none)), you don’t really have “vocal technique” at all, you just sing however you do.
The purpose of training the voice is to give you skills you wouldn’t have if you didn’t seek them. That includes expanding your range both up and down, expanding your dynamic expression (both louder and softer), being able to lengthen the time you can easily exhale during a sustained phrase, and being able to control the volume while you extend it, up to and including getting louder at the end or when you go up or both. You need to feel that you are singing easily and freely and that the sound responds well and that you can feel emotional while singing and that the emotion is reflected in the sound without you having to “make it emotional”. You need to be able to go very quickly or very slowly without issue. You need to be able to sing in a variety of tone qualities and colors in order to be effective in various contrasting styles. You need to look and feel congruent with the words and music while you sing. Trying to control your diaphragm isn’t going to help you do any of these things.
Somatic Voicework™ is functional training based on practical application, one person at a time. Everyone is the same and everyone is different. All voices are unique and all people are distinctively themselves but everyone has two vocal folds and a larynx, a pair of lungs, ribs and abdominal muscles. Vocal function is the same for any human being but vocal output is unique to the person, the age, the background, the training, the music, the interests and many other things.
There are a lot of people out there calling themselves singers who have no clue about the above. Some of these people also teach. (Unfortunately.) If you do not understand what I have written here, and you either sing or teach, you have, in my opinion, a moral obligation to learn about these things.