This guidance of the voice by the ear is incessant. It must not be understood that the mental ear simply conceives a single tone, and that the vocal machinery then operates without further guidance. All the characteristics of the vocal tones,--pitch, quality, and power,--are constantly changing. These changes require corresponding changes in the muscular adjustments. The muscular contractions in turn are guided by the demands of the mental ear. As a psychological process, singing may therefore be analyzed as follows: The singer mentally sings the composition. In response to the ever varying demands of the ear the vocal organs adjust themselves to produce actually the sounds thus mentally conceived. The singer listens to these sounds and at every instant compares them to the mental conception. If the tones actually produced fail to correspond exactly to those mentally conceived, the singer instantly notes this variation and bids the vocal organs to correct it. The ear has therefore a dual function in singing. First, the mental ear directs the voice in its operations. Second, the physical ear acts as a check or corrective on the voice. To sum up the psychology of tone-production, the singer guides or manages the voice by attentively listening to the tones of the voice. This is the only possible means of vocal guidance. The voice and the ear together form one complete organ. But we are still apparently as far as ever from the specific meaning of the correct vocal action. That the voice instinctively obeys the commands of the ear may be true theoretically. In actual practice we know that this does not by any means always occur. Singers are often unable to get the desired results from their voices, even when they believe themselves to rely on the sense of hearing. There must therefore be some influence which under certain conditions interferes with the operations of the vocal organs. The problem of tone-production is thus seen to be one of psychology. It narrows down to this: What can interfere with the normal action of the voice and prevent the vocal organs from instinctively responding to the demands of the ear? A satisfactory answer to this problem will be found only by a consideration of all available knowledge of the voice, both empirical and scientific. This forms the material of the final division of the present work. Part IV VOCAL SCIENCE AND PRACTICAL VOICE CULTURE CHAPTER I THE CORRECT VOCAL ACTION