As the strength of the tone depends upon the amplitude of the waves of sound, they, in their turn, depend upon the structure of the organ of singing, and of the parts of the mouth serving as a sounding-board or resonant apparatus, but, above all, upon the skilful management of the vibrating air. And although a fine timbre of the tones and due skill in increasing the amplitude of the vibrations may cause the voice to appear fuller and stronger, yet it is not in our power, when once the vocal organs have been fully developed, to make a strong voice out of a weak one.
Always to strike the true pitch fully and clearly requires persevering attention, as well from the teacher as from the pupil. And long practice is often required before the intonations become as pure as is indispensably necessary to good singing. For only upon the basis of a full, pure tone is a beautiful timbre (_Klangfarbe_) possible.
But the most important thing in the culture of the voice is the timbre of the tones, for _here it is in our power to form out of a sharp, hard and disagreeable voice, a voice sweet and pleasing_.
We have seen that the timbre is dependent on the forms of the vibrating waves, and the different degrees of strength and number of the over-tones arising from these forms. It has been further shown that the simple round form of the waves of vibration produces the softest, fullest timbre. By this form the fundamental tone is the strongest, and the over-tones are heard ascending to the third octave with decreasing degrees of strength. Such a tone is natural to certain voices. In most cases it must be more or less acquired.
1. By controlling and correctly dividing the air or breath as it is expired;
2. By a correct direction of the vibrating column of air; this is done by the right touch (_Tonansatz_);
And, 3. By a very distinct, quick and elastic _touch_.
By a too great pressure of the breath, the form of the waves of sound most favorable to a good tone is disturbed. One then hears the high over-tones sounding strongly up to the sixteenth, while the lower over-tones with the fundamental tone sound weak or not at all. Thus the tone takes a shrill, sharp and disagreeable sound when the form of the vibrating waves is more or less disturbed by too great a pressure of air. Too little breath deprives the tone only of its strength, but not of its agreeable sound.