During my research for the new level of Singing Lessons for Little Singers that will be coming out, I came across this wise advice from “The Child-Voice in Singing” by F. E. Howard, published in 1895.
[W]hile it is possible to develop the adult voice very considerably in power, range and flexibility, we ought, in dealing with children’s voices, to adopt those methods which will protect weak and growing organs. The aim is not more power, but beauty and purity rather. It should not be inferred that beauty of tone is not equally the aim in culture of the adult voice, but in that case it is consistent with development of strength and brilliancy of voice, while with young children it is not. If the tone is clear, beautiful, well poised, and under the singer’s control, then the training is along safe lines. If the tone is bad, harsh, pinched or throaty, then the training is along unsafe lines. When the parts act harmoniously together, and there is a proper and normal adjustment of all the organs concerned in the production of tone, the result is good. Bad tone follows from the ill-adjustment of the parts concerned in voice production. It is the office of the teacher to correct this ill-adjustment and bring about a perfect, or nearly perfect functional action. The teacher must judge of the proper or improper action of the parts concerned in tone production by the sense of hearing. No accumulation of scientific knowledge can take the place of a careful and alert critical faculty in training voice. Tone color must guide the school teacher in determining register as it does the professional voice trainer.