What, exactly, is training for the voice anyway? We all learn to speak by listening to our parents or caregivers by the time we are about two. Our genes determine our anatomy — how long the vocal tract is and how wide it can be, the length and thickness of the vocal folds, the size of the jaw, and mouth, etc. Some people grow up in circumstances where the voice is used energetically and some don’t. Some families are musical, some are expressive, some are performers — it varies so much. Why does anyone need training anyway?
It depends. If we speak about training in the sense that it coaxes the voice to go beyond its own natural tendencies, and prepares it to stand up to doing things no one’s voice was ever meant to do (like singing 8 times a week in a Broadway show), then we are discussing an atheletic development. It seems that music has always taken the voice somewhat beyond speech, although exactly how much has varied widely. Theatrical speech, however, also used to demand a lot from the voice that wasn’t exactly the same as conversation at dinner, but much of that kind of skill is disappearing, since virtually all professional (and a lot of amateur) theater is now amplified.
Based upon science, loud sounds and high notes need more air to be produced. The only way to get more air is to take a bigger (deeper) breath. If the air pressure inside the lungs isn’t sufficient, it needs to be pressurized so that it can be high enough to get the job done. Seems pretty simple, then, to figure out that a person needs to find a simple, easy and quick way to breathe in a lot of air and use it judiciously while sound is being made. The two parts of the body that logically would be involved with this process are the lungs and the belly. One could include the chest/ribs and the entire abdominal area, but the further away we go from those areas, the less direct the activity becomes. It also stands to reason that if the chest cavity is collapsed due to poor posture, not much air is going to go into the lungs. So posture figures significantly into the inhalation process.
If we decide that making continuous sounds is unusual (speech starts and stops), and if we also conclude that making continuous sounds primarily on vowels on specific pitches and volumes is also unusual, (that’s what vocal music does) maybe even very unusual, then we would have some good reasons why we would need to do something to acclimatize the voice to executing these tasks comfortably. If you just kept making such sounds, over and over, at increasingly loud volumes, you would be training the voice, and indirectly the breathing. That, in fact, is what self-taught singers do and in a lot of cases it works very well.
The problems come, then, when the above doesn’t work well, doesn’t work fast enough, or actually causes a set of problems. For instance, one could just lose one’s voice doing the above, and keep losing it over and over, unless you figured out something about what you were doing to cause the problem. Some folks can do that, and some can’t. It isn’t so much that there is just one way to train the voice, or that one person has found “the” answer, it is that the body (voice and breath) seem to like a certain way of working and not like other ways. Understanding how to take the voice beyond its natural boundaries and tendencies in a way that isn’t going to cause problems isn’t effective when it is just a random process of trial and error. In the case of quite a few singing teachers that is exactly what it turns out to be. Figuring out that you really cannot force the body to do anything that is not in its best interests, because sooner or later it won’t hold up, is just a question of common sense.
A great deal is known about exercise physiology. We know that straining the neck happens frequently while doing stomach “crunches”. Many atheletic trainers have modified stomach exercises in order to avoid this negative side effect. A good singing teacher is going to do the same thing with vocal exercises, so that the student will understand how to go beyond the normal demands of speech and simple singing, and into vigorous vocal expression without strain.
Because that is so, many people can teach singing effectively, with or without an organized method. For those who haven’t had time to figure out a variety of approaches and test them in order to see what kind of results they produce, learning about effective methods that someone else has developed and tested over time seems reasonable. As long as the exercises and attitudes work, as long as they are useful, as long as they get to the goals of the singer and do so without violence or harm, to the body or mind, the proof is in the doing.
Training that prepares the voice for any extended behavior is good. Training that is directed towards helping the singer do whatever kind of style they choose is good. Training that takes the voice into only one kind of sound or one way to breathe, is not.