In working on a short article for submission to Classical Singer magazine, I've reached an impasse in my thinking. Before I can continue writing my article, I have to clarify for myself the relative roles of conscious action and reflex action in processes like singing.
It's clear that some muscles I can move at will; I can contract my biceps, for example, in "making a muscle." Other muscles, like my diaphragm, do not seem to be operable at will; I cannot move my diaphragm up and down, for example. (If you think you are doing just that, it's probably your ab muscles you're moving, but that's another blog posting....)
These categories are not black and white, however. When I pick up my coffee cup, my biceps contracts (along with a lot of other muscles) with no command coming from me to do so. Just my intention to bring some mildly caffeinated beverage to my lips is enough to invoke the necessary muscle contractions for raising the mug.
I can also indirectly affect the activation of my diaphragm, stopping its motion by deciding to hold my breath, or changing its rhythm by breathing faster or slower. In these altered forms of breathing, I assume that my diaphragm is moving differently, although I can't feel it directly. (There aren't any sensory nerves providing a feeling sense in my—or your—diaphragm.) In other words, I can't move my diaphragm in a particular way, but I can cause it to move in that way by changing my breathing intentions.
A little experiment I just did convinced me that it is preferable whenever possible to let reflex run the show. I twice picked up pillow that was lying beside me on the couch. The first time I just decided to pick it up and let my body do the necessary muscular contractions to achieve that. Easy! The second time, I tried identifying which muscles would need to contract and to contract them so as to lift the pillow. I immediately froze up this second time, not knowing which muscles to activate for this "simple" movement, or in which order. The pillow stayed where it was, while my arm and neck got really tense. Eventually, I was able to make the pillow move a short distance, jerkily, with a huge expenditure of mental and muscular effort.
Try it out for yourself before reading on. Pick up any handy object in the two ways I've described.
How did that go? I am going to assume that you were not much more successful that I was at lifting the object by directly commanding your muscles to contract. But you probably had no trouble at all lifting it by simply intending to do so.
It seems that the subconscious part of our brains is highly skilled at bringing about the appropriate muscular coordination for picking up objects. . .and, presumably, all other activities. Like singing. All I need to do is have a clear intention of what I want to accomplish—I wish to sing a medium-loud middle C on the vowel [ah], for example—and my subconscious brain will elicit the correct response from all the muscles involved in the activity. Thank goodness I don't have to consciously command the jaw-opening, palate-raising, vocal-cord-activating, and breath-expelling muscles (whichever ones those may be!) to do their jobs; I would likely make as much a mess of all that as I did with commanding my arm to raise the pillow.
Of course, I might be interfering in some way with the free response of one or more of the muscles needed to sing my [ah], in which case I have to figure out how to stop interfering. That's the subject of my article for Classical Singer, to which I will now return.
Thanks for helping me sort this out.