As the voice is guided by the ear, the first requirement of a singer is a keen sense of hearing. For a keen ear to be of benefit, the student must learn to listen to his own voice. This is not altogether an easy matter. For one to learn to hear oneself justly and correctly requires considerable practice. The singer is placed at a natural disadvantage in listening to himself. This is due to two causes. In the first place, the direct muscular sensations of singing are so complex, and so distributed about the throat and face, that the singer's attention is apt to be divided between these and his auditory sensations. Second, the sound waves are conducted to the ear internally, by the vibration of the bones of the head, as well as externally, by the air waves. The internally conveyed vibrations are a rumbling rather than a true sound; the only true tone is the external sound, heard by the singer in the same way as by a listener. Yet the attention is more apt to be taken up with the internal rumbling than with the external tone. Every vocal student must be taught to listen to himself, to disregard the muscular sensations and the internal rumbling, and to pay attention only to the real tones of his voice. Throat stiffness greatly increases the difficulty of listening to oneself. Both the muscular sensations and the internal rumbling are heightened by the increased muscular tension. A stiff-throated singer confounds the muscular with the auditory sensations; the feeling of muscular effort also makes him believe his tones to be much more powerful than they really are. _The Acquirement of Skill_ Skill in the use of the voice is acquired solely by practice in singing. Only one rule is required for the conduct of vocal practice, that is, that the voice thrives on beautiful sounds. Musical taste must always guide the vocal student in practising. The voice cannot well do more than is demanded by the ear. If a student is unable to distinguish a correct intonation, his voice will not intone correctly. A student must hear and recognize his own faults or there is no possibility of his correcting them. He must be familiar with the characteristics of a perfect musical tone in order to demand this tone of his voice. In the student's progress the ear always keeps slightly in advance of the voice. Both develop together, but the ear takes the lead. The voice needs practice to enable it to meet the demands of the ear. As this practice goes on day by day the ear in the meantime becomes keener and still more exacting in its demands on the voice.