Richard, this "pretentious crap" works if you understand it. The diaphragm, the main muscle with which you breath (check a good book on human anatomy) is semi-voluntary. Which is to say, most of the time you don't have to think about it, it just does its job. But it can be controlled—indirectly.

Lots of people are shallow breathers, and the chronic shallow breather who attempts to sing is going to find himself or herself constantly running out of breath before a reasonable breathing point comes along (you can hear this in a lot of pop singers—and in folk singers as well—when they have to grab "catch-breaths" in mid-phrase and sometimes in mid-word). When these folks breathe, the diaphragm does move, but not to the extent that it can. Usually the person's ribs expand a bit and sometimes their shoulders actually move a bit when they breath, but this provides a very weak base for singing.

Have you ever watched the abdomen of a dog when it's asleep? Or a baby? Natural breathers, without tension. When you "sing from the diaphragm," you haul in enough air that your abdomen moves out and your lower ribs expand, and you fill your lungs. It should actually feel like you're filling your abdomen as well. But don't suck in so much air that you overfill your lungs. Once you have a good lungful of air, you can actually "set" your abdominal muscles (and indirectly your diaphragm) and sing a long phrase without having to interrupt it for "catch breaths." If you can sing long phrases, you can decide where to breath so the song makes sense (called "phrasing"), and not have to worry about when you can breath next as you are quickly turning blue. Good breath control ("singing from the diaphragm") and a relaxed, open throat are the basic fundamentals of being able to sing well.

Before you start singing, if you consciously relax your shoulders, take a couple of good, deep breaths (all the way to your belly-button), yawn a couple of times, and wobble your jaw a bit to make sure it's relaxed, it will improve your singing quite a bit.

Opera singers (and opera and lieder [art song] are the two most technically difficult and physically demanding kinds of singing) concentrate a lot on good breath support, i.e., "singing from the diaphragm." They also keep their throats open and relaxed. That's why they're able to sing flat-out for a couple of hours, live to tell about it, and come back and do it again a day or two later. And keep doing it for years.

Don Firth