One of my favorite hobbies is singing. I never had any talent for it, but through a lot of persistence and study I’ve been able to progress to a level where I’m comfortable calling myself intermediate. As part of this journey I’ve read a lot of singing pedagogy material and heard all sorts of things said about the voice. It’s a pretty mysterious instrument because you can’t see it, and that means myths are more easily spread about the voice than about (for example) the guitar.
By far my favorite approach to singing technique is the one developed by Cathrine Sadolin in her book Complete Vocal Technique. It’s really different and way less vague than anything else I’ve found. She has her own terminology and avoids vague terms such as “belting” and “head voice” which makes things very clear. Sadolin divides the set of possible vocal sounds into four “modes” called neutral, curbing, overdrive, and edge. Neutral is usually soft and gentle (like a lullaby) and has no “metal” (hardness) in the tone. Curbing is moany (Stevie Wonder uses it often) and has some metal. Overdrive is shouty (Dave Grohl uses it a lot in loud parts) and Edge is a very twangy (think Axl Rose). These last two have a lot of metal. Each mode has its own rules about what volumes work best, and what vowels can be used.
The cool thing about this breakdown is that it appeals to physics geeks like myself, and allows for some interesting analogies. For instance, there is a concept of entropy in the CVT approach, which allows for the “laws of thermodynamics” of singing. An example of a “law of thermodynamics of singing” might be “most untrained males can only sing high pitches in neutral”.
If you consider all the variables that you might change in singing (volume, pitch, vowel, coordination of your breath [called “support”]) then the most forgiving mode is neutral. It works on most volumes (the only thing not allowed is being loud on low pitches), all vowels, and doesn’t require that you are very good at support. In other words, neutral occupies a large volume of vocal parameter space. It has a high entropy.
To use curbing on higher pitches you need to support properly and your vowel choice is more limited. There is a small range of volumes that work, from medium-quiet to medium-loud. Curbing has a moderate entropy.
To use edge on higher pitches you need to support properly and your vowel choice is fairly limited (you have to use a lot of “twang” so you are restricted to vowels that are “twanged”). You also generally have to be loud. Edge has a pretty small entropy.
To use overdrive on high pitches you need to support properly and your vowel choice is VERY limited (there are only two vowels allowed). You also have to be very loud. Overdrive has a very small entropy.
So, to achieve singing a high pitch in a “powerful” (not neutral) way, you need to ensure many variables are right, so that you end up in the small “target” region of parameter space that allows that sound to occur. Also, the size of the “target” in parameter space gets smaller at higher pitches. If you are off in one or more variables, you are most likely to make a neutral type sound, because that mode occupies a large fraction of parameter space. That’s why most untrained men can only sing high pitches in neutral. These aren’t my ideas. They are present in the book already, but I find it interesting to make the analogy with statistical mechanics.