CHAPTER IV
RESONANCE
In order to understand fully the position in Vocal Science assigned to the doctrine of resonance, it is necessary to trace the origin and the development of this doctrine. The old Italian masters naturally knew nothing whatever of resonance, nor of any other topic of acoustics. Yet the accepted theories of resonance in its relation to the voice are directly based on a set of empirical observations made by the old masters. The facts which they noted are now a matter of common knowledge. In singing low notes a sensation of trembling or vibration is felt in the upper chest; high notes are accompanied by a similar sensation in the head. How these sensations of vibration came to be made the basis of the theories of vocal resonance, and of registers as well, is an interesting bit of vocal history.
Although almost entirely ignorant of vocal mechanics in the scientific sense, the old masters were eager students of the voice. They carefully noted the characteristic sound of each tone of the voice, and worked out what they believed to be a comprehensive theory of tone-production. One of their observations was that in every voice the low notes have a somewhat different quality from the high notes. To distinguish these two qualities of tone the old masters adopted the word used for a similar purpose by the organ builders,--_register_. Further, they noted the sensation of vibration in the chest caused by singing low notes, and concluded that these notes are actually produced in the chest. To the lower notes of the voice they therefore gave the name "chest register." As Tosi explains it, "_Voce di Petto_ is a full voice, which comes from the breast by strength." For a precisely similar reason, viz., the sensation of vibration in the head felt in singing the higher notes, this portion of the voice was called by the old masters the "head register."
When the study of vocal mechanics along scientific lines was undertaken, in the early decades of the nineteenth century, attention was at first paid almost exclusively to the subject of registers. The questions then most discussed were the number of registers, the number of notes which each should include, and the precise point of production of each register in the chest, throat, and head. Garcia's _Mémoire_, dealing with the registers, was noticed in the preceding chapter. He showed that different adjustments of the tongue, palate, and larynx are concerned in the production of the various registers. This _Mémoire_ opened up a new line of observation, in which Garcia continued to take the lead. But the extending of the scope of inquiry concerning the registers did not result in any unanimity of opinion on the part of the vocal investigators of that time.
For a few years following the invention of the laryngoscope (1855), vocal theorists ceased their disputes about the registers, and awaited the definite results of this new mode of observation. When this potent little instrument was put within the reach of every investigator, it was believed that the mystery surrounding the registers was about to be dispelled.
One important consequence of the invention of the laryngoscope was the turning of attention away from the sensations of vibration in the chest and head. Each register was ascribed to a distinct mode of operation of the vocal cords, and for several years the terms "chest voice" and "head voice" were held to be scientifically unsound. But with the publication of Helmholtz's _Die Lehre von den Tonempfindungen_ in 1863, the sensations of vibration again received attention. These sensations were then made the basis of a theory of vocal resonance, which has since been adopted by the great majority of vocal scientists.
Until the publication of Helmholtz's work vocal theorists had known practically nothing of acoustics. The fact that the tones produced by the vocal cords are increased in power and modified in quality by the resonance of the air in the mouth-pharynx cavity came as a distinct revelation to the theoretical students of the voice. Helmholtz confined his experiments and demonstrations to the mouth-pharynx cavity, and investigated in particular the influence of this cavity in producing the various vowel and consonant sounds. But vocal theorists at once extended the idea of air resonance, and connected it with the well-known sensations of vibration in the chest and head. It was assumed that these sensations are caused by vibrations of the air in the chest and nasal cavities.
This assumption has been accepted without question by the great majority of vocal scientists. Both the chest voice and the head voice are now believed to owe their distinctive qualities to the reinforcing vibrations of the air in the chest and nasal cavities respectively. The mere fact that these vibrations can be felt is held sufficient proof of the statement. "In every true chest tone the resonance can be distinctly felt as a vibration (fremitus pectoralis) by the hand laid flat on the chest." (_Die Kunst der idealen Tonbildung_, Dr. W. Reinecke, Leipzig, 1906.) It must be observed that this is by no means a satisfactory scientific proof of the doctrine of chest resonance. This feature of the subject is reserved for discussion later.
The doctrine of resonance is now generally accepted as one of the basic principles of Vocal Science. It is stated, in substance, by almost every authority on the voice that "The tone produced by the vibration of the vocal cords, even when the laryngeal action is correct in every way, is weak, of poor quality, and without character. This tone must be strengthened and made of musical quality by utilizing the influence of resonance." The subject of resonance is always treated in theoretical works on the voice under the three heads of chest, mouth-pharynx, and nasal resonance. To these a fourth is sometimes added,--the sounding-board resonance of the bones of the chest and head.
_Mouth-Pharynx Resonance_
Considered strictly in its bearing on tone-production, the resonance of the mouth-pharynx cavity does not receive much attention from theoretical observers of the voice. The form assumed by this cavity is of necessity determined by the vowel to be sung. Aside from its function in the pronunciation of words, the influence of mouth-pharynx resonance on the tones of the voice is seldom discussed by vocal scientists.
As a rule, vocal teachers pay little attention to this form of resonance. The subject of enunciation is generally treated as distinct from tone-production strictly speaking. While the correct emission of the tone, in its passage from the vocal cords to the lips, is considered a very important topic, this feature of tone-production has no reference to resonance.
One exception must be made to the statement that no attention is paid to mouth-pharynx resonance. This is found in an interpretation of the empirical precept, "Sing with open throat." Several vocal theorists take this precept literally, and hold that it describes a function of mouth-pharynx resonance. According to their idea the cavity must be expanded to the largest size possible, on the theory that a large resonance cavity secures a proportionately greater reinforcement of the tone. "The greater the size of the pharynx, whether through practice or natural gifts, the stronger in proportion is the tone." (_Die Kunst der idealen Tonbildung_, Dr. W. Reinecke, Leipzig, 1906.) This theory is of course rather loose and unscientific. Still this idea,--a literal interpretation of the "open throat" precept,--receives much attention in practical instruction.
Only one muscular action has ever been defined by which the throat might be "opened." That is, the lowering of the larynx and the raising of the soft palate. Many teachers therefore direct that the throat be "opened" gradually in this way for the swelling of the tone. It is assumed that the power of the voice is developed by singing with the larynx low in the throat. This manner of instruction is, however, very loosely given. The supposedly scientific interpretation of the "open throat" precept shades off into a purely empirical application.
_Chest Resonance_
In no other topic of Vocal Science is the gap between theory and practice more striking than in the doctrine of chest resonance. Vocal teachers are in fair accord in believing the resonance of the air in the chest to be the most important influence in imparting power and "color" to the voice, and particularly to the lower notes of its compass. Students of singing are in almost all cases urged to acquire a proper command of chest resonance. But when it comes to telling the student how to learn to govern the chest resonance, the teacher has practically nothing to offer. No direct means has ever been found for causing the air in the thorax to vibrate; this cannot be effected, so far as has yet been determined, by any voluntary muscular action on the part of the singer.
This being the case, intelligible instruction in the use and management of chest resonance is hardly to be expected. Teachers of singing are obliged to fall back on purely empirical instruction on this topic. This usually takes the form of a description of the sensations experienced by the singer when producing tones in the chest voice. How this description of the singer's sensations is applied, is discussed in the following chapter.
_Nasal Resonance_
The lack of connection between the theories of vocal scientists and the practical methods of singing teachers is well illustrated in the subject of nasal resonance. A striking feature of all the discussions concerning the use or avoidance of nasal resonance is the fact that vocal theorists base their opinions entirely on empirical observations. The use of nasal resonance is condemned by almost every prominent authority on Vocal Science. Yet the only reason ever advanced for condemning nasal resonance is the fact that a tone of objectionable nasal quality seems to "come through the nose." This fact cannot, of course, be questioned. It is mentioned by Tosi, who speaks of the "defect of singing through the nose," and is observed by everybody possessed of an ear keen enough to detect the nasal quality of sound.
It is generally stated by vocal theorists that the nasal quality is imparted to the tone by the influence of the resonance of the air in the nasal cavities. In order to prove this assertion Browne and Behnke offer the following experiment, (quoted in substance): "Hold a hand-mirror flat, face up, just below the nostrils. Then sing a nasal tone; you will note that the mirror is clouded, showing that part of the breath has passed through the nasal cavities. Now sing another tone, free from the fault of nasal quality; this time the mirror is not clouded, which proves that no air has passed through the cavities in question." (_Voice, Song and Speech._) This experiment is simplified by other authorities, who direct that the nostrils be pinched by the fingers, and then allowed to open by the removal of the pressure of the fingers. A steady tone is meanwhile to be sung. It will be noted, according to these theorists, that with the nostrils open the tone is nasal, and with the nostrils closed the tone is not nasal. This proves to their satisfaction that a tone passing in whole or in part through the nasal cavities must be nasal in quality.
It must be noted here that these experiments are not in any sense convincing. A tone of objectionable nasal quality can be sung equally well with the nostrils either closed or open, and so can a tone free from the nasal quality.
In theory, the mechanical prevention of nasal resonance is very simple. It is necessary only to raise the soft palate in singing, and thus to cut off the expired breath from passing into the nasal cavities. Most vocal scientists advise that the singer hold the soft palate raised for every tone.
Practical teachers of singing pay little attention to the theoretical discussions concerning nasal resonance. The overwhelming majority of teachers are firm believers in nasal resonance, and make it an important feature of their methods. They believe that this resonance is the most important factor in giving to the tone its "point," brilliance, and carrying power.
So far as instruction in the use of nasal resonance is concerned, teachers owe but little to the mechanical doctrines of Vocal Science. No voluntary muscular operation has ever been found, by which the air in the nasal cavities can be directly thrown into vibration, and so made to reinforce the tones of the voice. Instruction in the management of nasal resonance is therefore similar to that in chest resonance. The teacher describes the sensations experienced by a singer who produces the exact quality of tone desired. Use is also made of special vowels and consonants, for (supposedly) acquiring command of nasal resonance. A description of this form of instruction is given in the following chapter.
_Sounding-Board Resonance_
The acoustic principle of sounding-board resonance, in its application to the voice, is discussed by several vocal scientists. It is usually treated under two heads: first, the entire body is looked upon as a sounding board, capable of reinforcing the tones of the voice under certain conditions. Second, the bones of the chest and of the head are thought to be thrown into vibration, in sympathy with the vibrations of the air in the chest and nasal cavities respectively.
The importance attached by Howard to the sounding-board resonance of the entire body has already been noticed. Aside from the teachers of the Howard system, very few masters pay any attention to this feature of vocal reinforcement. Those who do so have no difficulty in dealing with the subject. When the singer stands in the position generally considered correct for singing, the body is said to be in the position most favorable for securing the benefits of this form of resonance. For this no special rules or exercises are needed.
Very little attention is paid, in practical instruction, to the vibrations of the bones of the resonance cavities. Each cavity is treated as a whole; the fact is only occasionally mentioned that the bones inclosing the cavities may vibrate, as well as the inclosed air.