VOCAL QUALITIES. 491 



1. Perfect elasticity and clearness of edge of the vocal cords, 

 and freedom from all surface irregularity, such as would be caused 

 by thick mucus adhering to them, or any abnormality. 



2. The cords must be very accurately adjusted, closely approxi- 

 mated together, and kept parallel, almost touching each other 

 evenly throughout their entire length. 



3. The cords must be held in a certain degree of tension, or the 

 vibration does not produce any vocal tone, but simply a raucous 

 noise. 



4. The air must be propelled through the glottis by a forced 

 expiration. The normal expiratory current is too gentle to give 

 the necessary vibration. After the operation of tracheotomy, the 

 air escapes through the abnormal opening, and sufficient pressure 

 cannot be brought to bear on the cords, so no vocal sound can be 

 produced, and the person speaks in a whisper, unless the exit of 

 air through the tracheotomy tube is prevented by placing the 

 finger temporarily upon the opening. 



PROPERTIES OF THE HUMAN VOICE. 



In the voice we can recognize the same properties as are noted 

 in other kinds of sound. These are quality, pitch and intensity. 



(1.) The quality of vocal squnds is almost endless in variety, 

 as is shown by the vocal capabilities of different individuals. 

 The quality of tone of any musical sound depends upon the rela- 

 tive power of the fundamental note, and of the overtones that 

 accompany it. The less disturbed the fundamental notes are by 

 overtones, the clearer and better is the voice. This difference in 

 quality of the human voice depends upon the perfectness of the 

 elasticity, the relation of thickness to length, surface smoothness, 

 and other physical conditions of the cords themselves, and the 

 exactitude with which the muscles can adapt the surfaces. For 

 singing well, much more is necessary than good quality of tone, 

 which is common enough. The muscles of the larynx, thorax 

 and mouth must be all educated to an extraordinarily high 

 degree. 



(2.) The pitch of the notes produced in the larynx depends 

 upon, first, the absolute length of the vocal cords. This varies 



