The vocal organs cannot, as we have shown, be trifled with. It is of vital importance, therefore, to the student, that his voice should be thoroughly diagnosed before fully entering on his studies, since a very slight error in determining the pitch is sufficient to undermine the physical powers of the vocal organs, and render their successful training impossible. It is to be feared that the ruin of good voices through this cause alone is great and constant. It is of common occurrence, to hear So-and-so spoken of as having studied as contralto under Signor A, and afterwards as mezzo-soprano under Herr B, or as soprano under Herr B, and mezzo-soprano under Signor A. In the case where the student possesses exceptionally great physical powers, he may for a time stave off the evil day; but eventually come it must, and then the fall is but the greater. And yet, to diagnose the pitch of a voice is not so difficult a matter; for, if the voice be cultivated within its natural limits, the muscles gradually acquire all those conditions so necessary to the proper working of the vocal organs, and the voice, as a consequence, becomes more and more musical. It gradually increases in breadth and smoothness, and, at the same time, it gains in power and mellowness, while the necessary effects are produced with the least amount of fatigue. For the first month, then, or so, the teacher requires to give his constant and best attention to the survey of his pupil’s capacities, and individualities, as any carelessness on his part at this period of his pupil’s career may be sufficient to irreparably damage the voice.

Barraclough, Arthur. Observations on the physical education of the vocal organs. Vol. 2. 1876.