Viardot-García's Method
Mme. Viardot always commenced her lesson with an exercise in breathing. According to her principle, the full breath so filled the lungs that the chest elevated and distended with air, while the muscles of the abdomen drew in slightly.
Her exercises began in the middle of the voice, upon the Italian a (ah) pronounced well forward in the mouth—which, by the way, she wished very wide open. They were always sung piano, with a light elastic tone, invariably with the head voice.
After one or two breaths, she would have me begin on a full chest, sing one of the exercises through several times until my breath was exhausted, after which she would have me stop, breathe deeply twice or thrice, and then repeat the same exercise, or else pass on to the next.
Mme. Viardot required that every tone should be pure and even and in perfect tune—a point to which she devoted extreme care.
If, during my lesson, for any reason an exercise was still imperfect after one or two attempts, she would pass on to the next, saying, "You must not force yourself." She made no rules as to diet or exercise, but wished me to practice by the half hour—in all, three or four times a day.
The text above—which gives the reader quite a bit of information about Viardot-García's method of breathing—was written by an anonymous student of Pauline Viardot-García in a beautifully produced magazine, circa 1896, which I found a number of years ago while searching Abebooks. The main thrust of the article is about singing coloratura, and includes a facsimile of the exercises given to the writer, presumably a woman as indicated by notation on the page ((Viardot-García's main students were women, though she did teach a few men, including her grandson Albert).
Back to Viardot-García's breathing method.
If you click on Louise Hérittte-Viardot's tab (Viardot-García's daughter), you will find an essay which includes an identical description of breathing method as realized by a very simple and often overlooked old school teaching: deep breathing through the nose.
Here's the deal: You can't obtain the action described above if you don't first shut your mouth when you breathe! Does this mean you have to breathe through your nose when you sing? Of course not. It does mean, however, that you have to retain the feeling and action of the breath that is learned with the mouth shut when the mouth is open.
Is this so hard? Not really. But experience reveals the majority of students do not give enough attention to the matter. That may be why Viardot-García had her students breathe consciously between exercises. The old school kept things simple, knowing that it's not what you know that's important, but what you do, the brain and voice needing action rather than abstraction. Towards that end, students of the voice are encouraged to incorporate the teachings on this page with those found in my previous post, keeping in mind that feelings (proprioception) are facts.
Obtain the right facts and you can sing.