The point of understanding vocal function is to also understand how to apply it in a useful, simple, easy and precise way to vocal production. Otherwise it is just more words that are no better than “place the tone in your eyebrows” or “support the sound from your diaphragm”.
In order to apply functional exercises you have to hear vocal function and see physical behavior (unless you are a medical doctor who has a scope to look inside the throat). That means that your ears have to become very sharp and that you have to have a specific intention for your listening as you listen.
Anchoring listening in registration is the first place to begin to perceive function. Beginning teachers have to learn to listen this way. Register quality is generally very discernible but only after you are used to it. In rare cases it can be camouflaged by the vowel sound or by volume extremes, but the more experience you have as a skilled listener, the better you will become in distinguishing the register quality for itself.
Further, when you can do that, it will be much simpler to hear what is not registration and that allows you to figure out where and how vowels become distorted, pitch goes astray, breathing isn’t grounded in the body and a host of other things. When you get a balance of registration across the break (see previous posts) and the vowels are not distorted, the volume is regulated by steady exhalation pressure and you still have “problems”, you can start to assume that the issues might be at the level of the vocal folds. In other words you will hear possible vocal pathology as being distinct from vocal mechanics. If you get that far as a teacher, you can consider that your skills are becoming more expert.
However, if all you can do it hear what’s wrong and you do not know what to do about addressing it, then you have only gone 50% of the way to helping the student improve her singing. You must know how to configure a vocal (music) exercise, choosing a pitch range, a volume (from pp to ff), and a vowel sound on a musical pattern in order to get from point A to point B. If you only guess at these exercises, you can be in the right ballpark but waste a lot of time. If you have a pretty good idea of what you want to impact and a pretty good idea at what kind of exercise will get you there, you can save time and help the student experience results without excess struggle or effort, at least most of the time.
These skills, needed by every teacher of singing, are not easy to acquire and some people never develop them. They gather a lot of intellectual information, they learn a bunch of things about music, voice and science, but they fail when it comes to the art of teaching and the bridge between that which is grounded in physical function and that which comes from the heart. The point of vocal technique skills is to marry the response of the voice and body to the imagination of the mind and the feelings of the singer. A teacher who can do that is a true teacher, and an artist. The first desire you must have if you would reach this goal is to get there.
I have configured Level II to give you tools to do this work. If you want to get better, please use them.