Vowels, Vowel Formants and Vowel Modification
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Vowel modification is an intentional, slight adjustment made to the sound (acoustics) of a vowel, by altering the basic way in which a vowel is articulated, with the goal of attaining more comfortable and pleasing tone production, especially in the higher part of the singer’s range. It is a conscious equalizing of the ascending scale. Some singers make these vowel modifications naturally and correctly, without even being aware them. Many singers, however, resist the natural tendencies of the voice, struggling to sing vowels exactly as they sound in speech all the way to the top of the voice’s range because they believe that they are supposed to. It then becomes necessary for them to learn the subtleties of singing vowels in the upper extension.
In a futile attempt to promote better blending of voices and clarity of diction within their groups, some ill-informed choir directors and teachers will instruct their choir members or students to use only speech vowels – vowels that are pronounced in the exact same way that they would be during speech, regardless of pitch. However, singing the exact vowels that are written by the composer is illogical and unnatural to the vocal instrument, as I will explain further in the following sections. Insistence upon singing the vowel written on the page will inhibit or prevent the natural ability of the singer to find the modification that serves the needs of the music and the voice.
By avoiding vowel modification as part of their technical training, voice teachers and singers ignore a means of producing a more resonant, carrying tone, and a more healthy, efficient way of achieving it, not to mention more control over dynamics and more ease in upper range singing.
A failure to correctly modify vowels throughout the changing scale will inevitably result in problems such as the inability to stay in tune in the area of the register breaks (passaggios) – faults in singers’ hearing are seldom the root cause for unintentional pitch deviations – other assorted intonation problems, adverse effects of consonant production on formant tuning and tone quality, resonance problems across the range (imbalance), an inability to sing at a soft dynamic level without losing the fundamental of the pitch, breathiness in the middle register, an inability to ‘cover’ (protect) the tone, an inability to access the head register, poor breath management and unclear diction and blending difficulties. All of these technical problems create a faltering and inept performance, since singers who are experiencing register problems find it difficult, if not impossible, to handle the musical and vocal problems that occur at the passaggios, and since imbalance of tone and an inability to sing at different dynamic levels limits the singer.
To avoid these artistic limitations, the proper muscular activities need to become almost reflexive. During singing, good interactions between the vocal folds, which produce the initial sound (‘buzz’) of the voice, and the vocal tract, which resonates that sound, are essential. These two parts of the vocal instrument should augment, rather than fight, each other.
Singers should sing vowels that free up the voice. When vowels are correctly modified, the singer experiences more comfort, the tone is more beautiful, and the air supply lasts longer. With the aid of vowel modification, singers will have fewer intonation problems, better resonance across their ranges, more carrying power, easier production of forte (loud) and piano (soft), clearer diction, and a much better blend. Furthermore, when the vocal tone is correctly formed by acoustical phonetics, the singer avoids many muscular problems, including hyperfunction and hypofunction, both of which may result in ‘stiffness’ of parts of the vocal tract, and can translate into hoarseness, register problems, unacceptable deviations from the pitch, limitations of range, color, and dynamics, poor vibrato, as well as other malfunctions and/or dysfunctions.
In my view, vowel modification is linked to two major aspects of singing: acoustics (including optimal resonance, balance of tone and smooth registration) and protection of the vocal instrument through correct and healthy laryngeal adjustments. In singing, one must learn to coordinate the acoustic and physiologic events of vowel definition while at the same time taking into account the relationships (and adaptations) of speaking to the singing voice. Only when these factors are coordinated can balanced resonance, with the upper partials that give the professional voice its characteristic chiaroscuro (balanced) timbre, be fully realized. Below, I have attempted to discuss the concept of vowel modification from these two perspectives. (It is impossible to completely separate these two aspects of vowel modification, since one affects the other.)
The vocal instrument, like all other instruments, is responsive to the laws of acoustics. When the vocal tone is correctly formed by acoustical phonetics, the singer creates a more pleasing, carrying tone, and avoids many muscular problems.
Vowel modification is an extended method of bringing the frequencies of the vocal folds and the vocal tract into accord with the various pitches and vowels. (This is known as the process of ‘formant tuning’.) Although it is possible for a vocalist to sing any vowel on any note within his or her range, some vowel forms will have better acoustical interactions with the vocal folds, aiding and amplifying their air pressures more effectively, while other vowel forms will have diminishing acoustical interactions with the vocal folds.
Modifications, which are achieved by making small adjustments to the size and shape of the vocal tract, persuade the resonator (vocal tract) to work efficiently, which creates optimal resonance and balance of tone. When the resonator adjusts so as to amplify the sung pitch, the vowels are, in that instant, automatically modified. For example, when female singers lower their jaws while singing [i] in the head register, they are modifying the vowel, as [i] sung with a slightly larger mouth opening will become a soft (or short) ‘i’, as in ‘bit’ and ‘fish’ or [ɛ], as in ‘bed’, if the jaw is lowered yet a little further. This kind of modification has positive effects on tone as well as vocal health, as it brings sung pitch and the resonance of vowels into their best relationship.
Some misguided teachers and choir directors instruct their students and choir members to sing all vowels using the same mouth shape throughout the range. However, it is impossible to maintain one vowel position at all pitches. If vowel positions are kept in a fixed state rather than modified, the voice will run into and out of resonance points, resulting in a sound that is out of tune, harsh, unfocused, and unsteady in vibrato rate.
Some choir directors and vocal coaches may ask their choir members and students to use what they believe to be ‘pure vowels’ - by ‘pure vowels’, they generally mean vowels that sound exactly as they do during speech - throughout a song in order to encourage clarity of diction. Although singing the vowel precisely as it would be pronounced during speech and exactly as the composer wrote it would be logical, it is not natural to the vocal instrument. Our ability to produce speech vowels (absolute language values) throughout the vocal range is a misconception because the vocal instrument simply does not work that way.
In fact, the more that the sounds of speech vowels are approximated during singing, the more inharmonic the voice will become. For example, some students vainly attempt to maintain the same spread mouth position of [i] that is used during speech above the upper passaggio, refusing to allow for the rounding that is necessary in order to facilitate a smooth transition into the head register. The voice inevitably begins to sound increasingly thinner, ‘squeaky’ and more strained, or it cuts out completely. The voice simply can't work the same way in the upper extension that it does in the lower range.
The most notable example of a singer’s inability to maintain vowels as they are spoken is when a female singer is singing notes in her upper range. Experienced composers understand this and write accordingly. High notes and very dynamically intense notes are usually musical events, not text events, and words are typically abandoned in favour of vocalises (wordless vocal ‘gymnastics’) during climactic moments in order to avoid having an uncontrolled and unattractive tone. On high pitches, the emphasis is on vocal skill - the beauty and impressive sound of the voice - rather than on diction skills.
Adherance to speech vowels produces tonal interferance because of the incompatibility of the vowels and pitches, which, in turn, destroys rather than promotes clear diction. Not only does avoiding natural acoustical adjustments create tonal imbalance, but it also risks numerous technical and health problems. Singers who utilize many non-harmonic sounds (speech vowels) that conflict with the written pitches do not sing as long because this practice is physically unhealthy. When asked to sing speech vowels in the higher parts of their ranges, singers will experience vocal unease and difficulty - including discomfort, a tone that is lacking in beauty, a serious diminution of the air supply, a reduction in carrying power, uncontrollable pitch inexactness (either flat or sharp, but most oftentimes flat) that are not controllable even when a singer is acutely aware of them, and deteriorating vocal health over time. The practice of singing only so-called ‘pure’ vowels is, therefore, illogical and unhealthy. (I will discuss this practice from a health perspective in the following section on vocal protection.)
Acoustically speaking, these speech vowels are not necessarily ‘pure’, anyway, as they may differ somewhat from speaker to speaker. In addition, speech vowels vary considerably depending upon regional accents, (as I’ve already discussed in the first few sections of this article). The results are, therefore, less than uniform and less than ‘pure’. This fact means that neither diction nor resonance will be aided by singing speech vowels. Whereas spoken vowel values vary according to languages and dialects, in singing, vowels must always be compatible with vowel pitch and the harmonic of the sung pitch. (This is one of the reasons why people can sing in a foreign language without an accent but cannot speak it without an accent.)
Regarding intelligibility of diction as it relates to vowel modification, research has shown that, once a voice reaches the pitches of its high passaggio, the human ear can no longer perceive the difference between that same voice singing one front vowel or another, one back vowel or another. Furthermore there are acoustic regions where more than one vowel intersect. This means that one vowel adjustment will sound like two or even three different vowels depending on context (surrounding consonants, etc.). (I have written more about the female upper register and why vowels can’t be easily distinguished at higher pitches in the article entitled Singing With An Open Throat: Vocal Tract Shaping, also posted on this website.)
Intelligibility, therefore, does not mean that someone is singing the spoken form of a vowel. Since the listener cannot perceive the difference between certain vowels that have similar qualities at high pitches, it makes no sense to attempt to sing a vowel that is incompatible with the sung pitch and that is more difficult (and possibly uncomfortable) to execute. Besides, at these high pitches, intelligible diction is still possible because it is the consonants (and their positions in relation to the vowels) that play a larger role in distinguishing words.
Even though a singer or choir director may resist natural vowel modification, this avoidance doesn’t change the fact that vowels cannot be sung as they are spoken. This is true throughout the range because every note has a different resonance necessity, and therefore a different formant balance due to its unique vocal tract configuration.
It’s important to understand that vowel modification doesn’t just happen in the high range of a singer’s voice (i.e., upper middle and head registers). A singer whose vocal resonance is even and consistently good from note to note – high or low, soft or loud – is changing the vowels semitone by semitone, and the vocal tract is constantly changing form. Good singers, whether consiously or not, depend on finding an easy adjustment, or modification, for the pitch. These modifications may not be easily perceived by the listener, and the singer may not even take note of them, but they do happen throughout the range, even within speech inflection range. In fact, vowels are naturally and effortlessly modified during speaking tasks, as inflection rises or lowers and as volume changes, although we are not aware of these subtle adjustments because they occur so commonly and instinctively.
The fact of the matter is that bad sound is far more noticeable than slight modifications of language values. It therefore makes sense to allow for natural resonance adjustments created by vowel modification.
Those experts who really understand the acoustics of the voice – acousticians - consider a pure vowel to be one that delivers ease, beauty, and resonance on that particular pitch. True vowel purity, then, is the optimum acoustical response for a given vowel. When the most resonant vowel on a particular sung note is found, it is invariably different from the one used in speech patterns.
Both vowels and sung tone have pitch. The pitch of the vowel being sung must be harmonic with the sung pitch, or there will be a weakening of the vocal fold vibrations, which may be accompanied by an ‘untuning’ of the tone. When the vowel is incompatible with the sung pitch, the singer may experience anything from slight discomfort all the way to actual pain, the tone will be anywhere from slightly less than beautiful all the way to actually ugly and unpleasant, and the air supply will be diminished radically because it takes more air to sustain an inappropriate vowel. Inflexible language treatment – that is, insisting that all vowels be sung exactly as they would be spoken - tends to impair the musicality, expressiveness, and survival of voices. (This is why an unknowledgeable teacher who insists on treating diction inflexibly can do a great deal of harm to his or students by ignoring the laws of vibration and resonance.)
With acoustical vowels, the harmonic values of the pitch coincide with the pitch of the vowel itself. They therefore produce optimal amplification of resonance, giving the voice more size and carrying power, (which is especially important in unamplified singing), as well as a physiological feeling of well-being (versus a feeling of tension, discomfort or pain), vibrancy (‘ring’ and vibrato) and pitch centeredness - almost always, the use of acoustical vowels in singing produces tones that are in the centre of the pitch. Singing with the best relationship of the larynx (vibrator) and the vocal tract (resonator) is healthier (e.g., singers who use harmonic sounds, or modified vowels, sing for a long time because they are more therapeutic for the throat), more pleasing to the ears, and aids in breath coordination (lengthens the air supply).
The core of the vowel, which itself is achieved by specific articulatory definitions (e.g., the size of the jaw opening, the shape of the lips, and the position of the tongue), is also the core of the pitch when that vowel is sung rather than spoken. Each vowel has a quality that is unique to that particular vowel, a quality that names the vowel or makes it what it is. (Earlier in this article, in the Vowel Formants section, this quality of the vowel was referred to as its individual ‘fingerprint’.) The vowel core, then, is the identifying quality. It is also an acoustical phenomenon. For example, when the vowel is identified precisely, the resonance chambers of the vocal instrument are immediately re-shaped so that optimum amplification of the basic sound is achieved. The singer then has greater volume and potential for dynamic variation, as well as improved intonation and greater ease of production.
Also, the use of acoustical vowels aids, rather than detracts from, diction. Speech recognition, which all teachers and singers desire, is dependent upon the changing shapes of the filtering resonator tracts above the larynx. A knowledgeable teacher understands this delicate and ideal interaction, and can help his or her students accomplish a great deal by obeying the laws of harmonic pronunciation.
Vowel modification must be mastered in order to facilitate smooth transitions throughout the range - from low to high and from soft to loud. As a basic rule, the louder or higher, softer or lower a vowel is sung, the more it will migrate from its original version. Although modification is necessary for all voice types, the problem affects sopranos and tenors especially because they must reconcile with the higher frequencies and intensities of higher and louder tones, and a large resonating cavity is needed to avoid placing strain on the larynx.
Vowel modification (the use of acoustical vowels) is also important in the technique of formant tuning, since modifying vowels is done through making slight adjustments of the vocal tract (the resonator), which in turn changes the acoustical qualities and values of the sung vowels.
Resonance adjustments (acoustic shifts) should occur around D for all singers, although depending on the vowel modification involved, they may happen sometimes on C#. It does not depend on voice type, as acoustic shifts tend to happen in the same place within the scale regardless of the singer’s voice type (and gender). Vowel charts – see below - can be followed to accomplish the acoustic shift from formant 1 to formant 2 between specific areas of the singer's range.
Good acoustic shifts are especially important for the skill of seamlessly bridging the registers, as well as for accessing pitches above speech-inflection range (i.e., head register). This shifting is subtle, and takes place gradually throughout the scale. If it is left to occur only at the pivotal registration points (passaggios) where the muscular shifts occur, there will be a noticeable difference in the tone quality and in the vowel quality, and the shift will be made more noticeable by a register break. As I emphasized in the Blending the Registers section of Good Tone Production for Singing, anticipating the registration points and making subtle adjustments to the vocal tract a few notes ahead of time will enable the singer to safely and comfortably execute register changes.
The muscular shift, (associated with the passaggio), occurs at different places, depending on the singer’s voice type. It happens a little earlier (slightly lower in pitch) in dramatic voices and a little later (higher in pitch) in lighter or leggiero voices. Second formant tuning is more appropriate from F4# on, however, a lighter tenor will feel less stress singing a first formant dominant F4# than a heavier voice will. Regardless, the larynx will rise for an F4# sung in first formant dominance. The leggiero who keeps f1 (first formant) dominance up until A4b, like some do, will experience a more difficult shift when he finally does go to f2 tuning.
Voice pedagogues and acousticians have come up with practical systems for helping singers achieve correct vowel modification. One available tool for helping singers find the right tone balance while singing a vowel is a vowel modification chart.
Vowel modification charts have been designed to provide practical details of a system that allows singers to choose the vowel form that would give a compatible frequency with the pitch. Some teachers employ vowel charts to allow their students to aim for a specific modified version of the original vowel that will ultimately enable them to sing the notes with ease, comfort and greater tonal balance.
One such system can be found in Berton Coffin’s book entitled Overtones of Bel Canto. This particular chart is said to be extremely efficient and easily comprehended. Coffin’s chart makes it possible to train singers in the art of specific vowel modifications, and thereby teach them to find the Singer’s Formant - the overtone that gives the voice its ‘ring’ - instinctively. A simplified version of a vowel modification chart for the head register can be viewed in Vowel Modification In the Upper Range, below.
Such a detailed system for achieving ideal acoustic resonances for every vowel at every pitch may seem overly mechanistic in quality and tedious to some teachers and students, and they may attempt to avoid vowel modification as a result.
When a chart is used, many students try very hard to produce the ‘correct’ vowel sound at the right note, which may not necessarily be in line with their particular or individual acoustical production, and they become frustrated. Some students who are not naturally good with languages may struggle with distinguishing between the subtleties of certain similar vowel sounds and with pronouncing certain vowel sounds that have been adopted from other languages (e.g., the German ‘Ö’). They may also fail to accurately imitate these sounds when sung or spoken by their vocal instructors.
Nevertheless, using vowel modification charts can be effective for many vocal students. In the best-case scenario, a resonant vowel adjustment will yield sensations that the singer will come to recognize and reproduce easily as long as the instrument is healthy. Once the singer has a clear proprioceptive experience of first and second formant resonance, he or she will then be able to track formants more spontaneously and instinctively.
In my studio, I don’t typically use vowel modification charts, although I have used simplified charts from time to time to students who respond better to having clearly defined rules, steps and ‘how to’s’ about singing or who cannot find the natural adjustments of their vocal tracts easily despite having tried the other techniques that I have offered them. For most of my students, simply hearing (and watching) me demonstrate how vowels might become correctly modified throughout the range is enough for them to grasp the concept of vowel modification and then apply it to their own singing. I believe that every singer must find his or her own variation of the vowel that is most compatible with his or her own voice at every pitch.
It should be understood that a vowel chart is a beginning not an end. Vowel modification is worthless if the phonation mode is not efficient – that is, if the student is not singing with good technique to begin with.
Another alternative to using a vowel chart might be providing students with exercises that are designed to help the singer find the vocal protection and experience a smooth blending of the upper register by altering the vowel at clearly outlined points during the exercise. For example:
Notice that the pitch at which the vowel modifies is slightly different on the descent. This accounts for the slight differences in how notes are managed on the way up the scale versus on the way down.
The above exercises must be performed with an open acoustical space, with the ‘UH’ (as in the word ‘good’) feeling in the soft palate, not in the larynx, in order for them to be beneficial. While vocalizing, the singer should think a slight lift at the root of the tongue as he or she ascends into the upper range, along with a slight tilt downward of the larynx in the upper middle register. If vocalized with a high soft palate, these exercises will offer balance in the upper passaggio.
One exercise that will help to develop this open acoustical space involves starting a descending octave arpeggio from the upper note downward:
The feeling of 'UH' in the soft palate should be spoken while a clear [a] vowel is spoken with the tongue. If the back muscles are engaged at the onset, it will be much easier to start the high note. This mixing of the 'UH' and the Italian [a] will create a balance of what is called cover or vocal protection (see below) without muscular involvement with the tongue root. It will also discourage a heaving of the throat muscles.
Vocalizing on open vowels in the lower voice to more rounded vowels while ascending toward the upper range will encourages a proper alignment of the upper passaggio.
Vowel modification is also referred to as covering, vowel darkening and vowel rounding. The technique of modifying the vowels in the upper range ‘covers’ up the unpleasant stridency that characterizes an uncontrolled high note and protects that voice from strain and injury.
The vocal cover or protection consists of a coordination of several functions both in the lower body and in the throat. Each body function must be studied individually, and then coordinated. After this coordination is achieved, the singer can then perform without concentrating so much on vocal technique.
Vocal protection is connected directly to an acoustical release that is a result of a properly opened acoustical space (throat), as well as a healthy release of tongue. This free throat space is reflexive as the vowel is strengthened (strong vowel in the high and wide soft palate) and altered (modified) properly. (Read Singing With An Open Throat: Vocal Tract Shaping for more information and methods on achieving this ideal open acoustical space,) The correct laryngeal tilt in the upper middle register allows the singer to feel a release in the root of the tongue, thus allowing ease into the high range. The resulting acoustical release in turn allows for a healthy balance of upper and lower overtones within a singer's vocal production.
The skillful execution of singing hinges in part upon the physical events of vibration and resonation that are brought about by certain muscular activities related to the vocal instrument. If the proper muscular activities do not become almost reflexive, the singer will face numerous artistic limitations. These limitations may include register problems (most noticeable at passaggios, and often due to engagement of the laryngeal muscles in an attempt to shift the voice or make the voice 'flip' registration), unacceptable and seemingly unfixable deviations from the pitch (not usually caused by faults in the singer’s hearing ability), limitations of range, colour, and dynamics, as well as poor vibrato (oftentimes manifested as a vocal wobble, an unhealthy and overly wide vibrato rate that is usually accompanied by a depressed tongue), vowel distortion, loss of upper range due to a high-larynxed singing position, and a lack of ring in the voice, making breath management difficult.
Additionally, avoiding natural vowel modification leads to strain and tension, hoarseness, as well as other malfunctions and/or dysfunctions, especially during the production of high notes, because the singer’s larynx rises above the floating position, or is depressed below it, while the soft palate is pulled down. The solar plexus – a nerve plexus in the abdomen that is situated behind the stomach and in front of the aorta and the crura of the diaphragm (two fibromuscular bands that arise from the lumbar vertebrae and insert into the central tendon of the diaphragm) and contains several ganglia distributing nerve fibres to the viscera (internal organs) - will often become locked. Neck muscle tension may also ensue because the singer relies upon the biofeedback received from the resonance to know whether or not he or she is using correct ‘placement’.
Some schools of training teach a muscular cover, whereby the tongue is depressed in order to cause a sudden adjustment in the vocal mechanism. The neck muscles are often also engaged in an unhealthy manner. This sudden shift, which is often heard in male singers, (especially basses and baritones), is a futile attempt to access the high range using a retracting or pressing of the root of the tongue. The muscular cover does not produce a smooth transition between the registers since the voice looses its register blend and begins to sound like different voices rather than one smooth sound. In fact, it typically prevents a singer from accessing the head register altogether. If the upper passaggio is managed with tongue pressure, the problem of registration is made even more noticeable in the singer. Furthermore, the muscular cover is extremely dangerous, and is a particularly difficult habit to break, since it usually involves undoing years of built up tensions through the retraining of the tongue.
Many singers, both male and female, resort to using muscular pressure (usually using the tongue and neck muscles) instead of finding an authentic open throat and pharynx, where the soft palate is high, the back wall of the throat (pharynx) behind the tongue is wide, and the larynx is slightly lowered and wide. The interior pharyngeal space actually closes when a singer uses this of kind muscular cover, and tremendous pressure is then placed on the vocal folds by the root of the tongue. The singer becomes uncomfortable, and there is a hesitation toward free oscillation of the vocal folds. (To learn more about this incorrect technique, read Singing With An ‘Open Throat’: Vocal Tract Shaping.
If the muscular cover has been engaged, the singer must push a tremendous amount of breath pressure to force phonation when he or she wishes to sing higher notes. Too much weight is then dragged up through the middle register; that is, the lower mechanism of the voice is carried too high up in the scale. The pushing of breath pressure does not allow for healthy vocal fold adduction, which then leads to more and more pushing of breath pressure. The tongue then becomes tense at the root, creating a gag reflex at the back of the tongue. In turn, this gag reflex causes direct pressure at the glottis, making healthy vocal fold vibration impossible.
In order to achieve a protection of the voice, singers must use correct lower body support to hold back the breath pressure. (To read more about correct breathing technique for singing, please refer to the article about breathing on this site.) Studying the concept of ‘inhalare la voce’ (‘inhale the voice’), developed by 19th century Bel Canto teachers, can help a singer find better relaxation of the vocal mechanism and better breath management. This expression describes a feeling that the tone is coming to the singer, rather than being blown out of the singer. The feeling of the inhalation of tone assists the entire breath support in keeping the muscles of the body from collapsing or tensing up. The feeling of inhaling the tone allows the singer to produce a soft onset and balanced tone, activates head resonance and encourages the soft palate to remain high. Refusing to allow tension in the throat and lower jaw also allows the larynx to relax.
‘Cuperto’ is the Italian term for vocal covering. It is associated with an open acoustical space as well as the alteration of the vowel without using the tongue. (The tongue should always speak the integrity of the vowel – that is, it should maintain its normal position for the desired vowel - even if the vowel is altered in the pharynx.) If employed correctly, this concept of cuperto can protect the throat and encourage healthy singing. While the throat seems to be quite open, there is a narrow ring in the middle of the tone.
Healthy protection of the voice is more difficult to teach men than women because they have very developed (strong) throat and upper body muscles, and can push their way through some of the high range. However, more dramatic female voices may also go to the extreme in the study of the vocal protection. Lighter-voiced singers, both male and female, can also try to over-develop their voices by singing inappropriate repertoire or by ‘belting’ - a technique whereby the lower mechanism of the voice (e.g., chest voice) is carried up as high as possible, and higher than is healthy - mostly in an attempt to compete in a world that often holds the belief that ‘bigger’ voices are always better. (I will be posting an article on the technique of ‘belting’ in August of 2009.)
It is especially important for young singers to find this protection early on in their training. If trained properly at a young age, the singer can be saved from years of frustration and perhaps vocal damage leading to a shortened career. The major key in training younger voices is to make sure the upper middle voice is functioning in a healthy manner, with the correct laryngeal tilt aided by and open throat and vowel modification.
As mentioned above, it is important to encourage the larynx to remain low (in its "at rest" position) and relaxed in all singing, regardless of pitch. (Many teachers who teach belting techniques encourage their students to raise the larynx, and this technique can put a great deal of strain on the instrument because it doesn’t allow for healthy muscular shifts to occur.) However, the larynx itself does ‘tilt’ as pitch ascends in order to help elongate the vocal folds. The lower larynx actually aids this laryngeal tilting action of the cricothyroid musculature that is essential in stretching the vocal folds and allowing the singer to ascend to the higher range with relative ease.
The thyroid cartilage consists of two flat plates forming an angle anteriorly, which, among other things, acts as a shield for the vocal folds. The thyroid angel is about 90 degrees in males and about 120 degrees in females. Because the angle is more acute in males, the protrusion can often be seen and felt as the ‘Adam’s apple’. Posteriorly, each plate of the thyroid cartilage has two horns, or cornua. The interior horns form a joint with the cricoid cartilage as its posterior lateral part at matching facets on the two parts. This allows the cricoid to tilt over a range of about 15 degrees in an anterior-posterior sense with respect to the thryroid cartilage. The tilting motion plays an important role in controlling vocal fold tension.
Vocal fold length and tension can be controlled by rocking the thyroid cartilage forward and backward on the cricoid cartilage (either directly by contracting the cricothyroids or indirectly by changing the vertical position of the larynx), by manipulating the tension of the muscles within the vocal folds, and by moving the arytenoids forward or backward. This causes the pitch produced during phonation to rise or fall.
The protection of the voice results from this proper ‘tilt’ of the larynx in the upper middle register, resulting in open acoustical spaces in the soft palate, behind the tongue and behind the larynx. (In upper middle voice, the larynx should pivot or tilt slightly down and forward in order for head voice to function. The concept of the neck slightly widening for the middle register – the Italian ‘vomitare’ posture - will help with this laryngeal pivoting, as well, but it should not be taken too far.) This 'laryngeal tilt', coupled with proper alteration of the vowel, makes for a seamless and smooth sound throughout the low, middle, and higher registers, without muscular effort or too much push of breath pressure. There is an acoustical release in the upper passaggio, which sounds as though the singer could sustain the higher notes at all dynamic levels (e.g., loud, soft).
(A detailed diagram of the larynx can be found in Singing With An Open Throat: Vocal Tract Shaping.)
A healthy protection of the voice creates a smooth, balanced acoustical production that moves through the registers smoothly and effortlessly. There is a similarity of vocal colour (quality, or timbre), and the singer never has to struggle to move through the registers (e.g., no breaks in registration, no unpleasantness of sound, and no physical discomfort or pain). This basically consists of a healthy upper register transition so that the upper passaggio, (the core of it being high E-flat to high F-sharp for both males and females, although an octave higher for females), sounds like one voice even though there may be a slight difference in sensation in each half step of vocal range.
Correct transition in the upper passaggio must occur gradually, beginning in the middle register. Singers need to learn proper laryngeal function (e.g., the laryngeal tilt) in the upper middle register. This laryngeal tilt is aided by a 'rounding' or 'darkening' of the vowels - vowel modification. An awareness of these modifications aids the general efforts of counterbalancing. As pitch goes up, everything else must stay down (and remain relaxed). This, of course, includes the larynx. Darkening vowels helps the larynx resist the tendency to lift up along with the tone. By gradually modifying vowel tone a bit darker in upper phrases or on individual top notes, as needed, the larynx is coaxed just a little lower. The stabilized, normal position for the larynx on all well-sung notes, including high notes, is known as the floating position.
If the middle register is in balance, allowing for some alteration of the vowel through a slight change in the shape of the pharyngeal wall, there will be fewer problems as the singer approaches the upper passaggio. When the middle register is exercised correctly, there will be a smooth and even transition between registers around the high E, F or F#.
The study of rounding the vowels needs to be done slowly and carefully, paying strict attention to the slow and gradual rounding of the vowel forms. The mouth shape should be rounded toward an oval. Darkening of the vowels should only be done by increasing the acoustical space, not by pulling down the soft palate or the back of the tongue. These incorrect and unhealthy techniques cut out the upper overtones, and lead to inconsistency and frustration for the singer.
Most singers who have difficulty with the top of their voices either do not round the vowels at all, resulting in a spread 'smile technique', or they ‘overly-darken’ the vowels, which invites the tongue to depress the larynx. If either extreme is employed, the singer will experience tension in the upper register.
When a singer spreads the mouth opening while singing on the staff, (sometimes also referred to as a ‘spread position’, or ‘voce aperta’), the resulting sound is thin and throaty with very little true warmth of tonal quality. The singer also experiences problems in balancing registration, as wide open vowels will create a ‘crashing of the registers’ – a severe register break that occurs when the vowels are too spread. (The chest and head registers become very different in coloration and timbre.) Musicianship is then sacrificed to a great extent because the singer feels as though his or her voice is about to break at any moment. This dangerous feeling is caused by a lack of adduction, or vocal fold closure.
The Italian School often speaks of 'narrowing the vowels' at the passaggio. An oval shape of the mouth is necessary in order to accomplish this narrower feeling. Usually this is regarded as an important factor in the upper passaggio. However, it is also true in the lower passaggio. The narrower mouth opening with the corners of the mouth rounded into an oval shape will give a singer a much cleaner transition between these registers because the larynx assumes a lower position and the soft palate assumes a higher position, which then allows the vocal folds to approximate better, creating a fuller and more balanced sound in the lower passaggio.
Most of the lower male voices do not skillfully negotiate the middle register from F to A-flat. Usually this part of the voice is sung wide open (voce aperta), without addressing the concept of narrowing, rounding the vowels or the pivoting of the larynx - see above section. This wide-open singing makes for a common mistake that often leads to the vocal wobble (large, slow vibrato function). Tuning problems, usually flatting in pitch, result when the middle voice is not rounded enough because the singer is taking up too much vocal weight (thicker vocal fold mass) through the middle register, or zona di passaggio. If the vowels do not round, there is no possibility for the pivoting of the larynx in the middle register, a function that is critical to using the thinner edges of the vocal folds in the upper register (because it controls vocal fold length and tension). Many male students are unable to sing past A-flat because of this failure to narrow, or modify, their vowels. So long as they continue to approach this part of their range in the same incorrect manner, they will keep experiencing the same discomfort and inability to successfully sing above this pitch.
Some singers begin to round and darken the vowels too early in the scale, creating a distortion of both diction and timbre. The entire voice itself becomes darkened as the singer pulls down the back of the tongue. This practice is called ‘over-covering’, and it leads to a shortening of the higher register (either loss of or lack of high range).
Although acoustical modifications do happen within speech-inflection range - slight acoustical adjustments are made at every semitone - vowels shouldn’t be intentionally modified in the lower and lower-middle ranges. As I stated in Singing With An Open Throat: Vocal Tract Shaping, a singer needn’t do anything substantially different with the articulators while singing within speech inflection range than he or she would during speech. Modifying or darkening vowels in these ranges will create a muffled tone and a distortion of vowels.
The study of vowel modification in the head register is a major focus of students and vocal technique instructors. Correct vowel modification is necessary in order for the voice's full range to be developed.
Below is a sample of a vowel modification chart for the ‘five pure Italian vowels’ typically used in vocal training. The top row shows the desired vowel being sung, and the bottom row shows the approximate modified sound when the singer is in the head register.
Keep in mind that the change from the desired vowel sound to the head voice modification happens gradually, over several notes and not just at or above the upper passaggio, as slight acoustical adjustments are made by subtle movements of the articulators (mainly the jaw). This means that there will be intermediate vowel sounds produced between the upper middle register (or zona di passaggio in male voices) and the lower part of the head register. For example, [o] doesn’t suddenly turn into ‘AH’ at the passaggio. It gradually becomes the modified version over the course of several notes.
I often encourage my students to anticipate these changes a few notes ahead of time, so that they don’t carry the lower register, nor the acoustically unmodified vowels, up too high and then experience a register break when the laryngeal muscles have no other choice but to make a sudden shift in order for the voice to reach the next higher pitch. Anticipating the upper passaggio enables the singer to make appropriate acoustical shifts as the passaggio approaches, and thus allows the larynx to pivot correctly and the muscles to adjust more gradually in order to avoid a register break, as well as physical discomfort.
As an example, let’s examine how the vowel [i] might become modified as the singer ascends in pitch. As [i] is carried higher, it needs to gradually taper toward the sound of the German Ö. At the point where the acoustical shift begins to take place in the upper middle range, the vowel begins to gradually change to a short ‘i’ sound, as in the word ‘it’. This alteration may take place over a couple notes. At the place where the muscular shift happens (the upper or secondo passaggio), the vowel will generally begin to sound more like the German ‘Ö’. This change also happens gradually, over a couple notes. When students have difficulty mastering this German sound, I suggest that they aim for some form of [ε], as in the word ‘bed’.
Again, these modifications happen gradually over several notes, as the vowel slowly moves from more close to more open. Helping singers achieve mastery of the head register involves opening the closed vowels and closing the open ones. The process of opening the closed vowels essentially moves the vowel sound from tense to less tense, allowing for greater rounding. These changes happen when the singer allows the lower jaw to drop just a little more than it would when singing in the lower registers. For example, the vowel [i] is the highest and most fronted vowel that can be ideally produced by the human phonatory system. By gradually increasing the aperture (opening) between the tongue and the roof of the mouth, the intermediate positions (e.g., mid-closed [e] and mid-open [ε] can be established. This lowering of the jaw should not be excessive, and it should not be stiff or uncomfortable. The degree of buccal (mouth) opening will be affected by the vowel, the pitch, and by other dynamics of the note, such as volume.
Conversely, in the head register, more open vowels must become somewhat more close. The most diametrically opposed in position to [i] is the vowel [a], which is the lowest and most open back vowel. By raising the tongue from the [o] position, which is a mid-close back vowel, increasingly closer vowels will be obtained until the [u], the highest cardinal back vowel, is obtained.
Getting into head voice early enough (but not too early) in the scale allows the singer to release in the upper passaggio in such a way as to create a perfect blending of the registers. I'll often instruct my students to 'incorporate more head voice tone into the upper middle register'. The male singer vocalizing on the [a] vowel sound, for example, needs to feel an 'AW' starting around C-sharp4 and then 'UH', as in the word 'good', by the D or E-flat, depending upon the vocal fach. Notice that these modifications happen before the upper passaggio is reached. Feeling the 'UH' in the soft palate, not in the larynx, will discourage the larynx from becoming depressed.
If the rounding of the vowels does not happen around the head voice transition, then the singer is pulling up too much weight (thicker vocal cord mass). The resulting gag reflex that builds in the root of the tongue forces the solar plexus to shake in an attempt to force phonation. Remember that any vowel alteration must be done with the feeling of the vowel strength in the soft palate, mirroring that strength of vowel at the folds. Typically, if vowel space is only imaged in the larynx, then the tongue will often depress.
To create vowel modifications, a singer must learn to mentally hear one vowel sound while singing another. By simply thinking about a certain vowel sound - the desired vowel, not the modified version of it - a tiny bit of that vowel sound will blend into the vowel that is actually being sung. The singer needn't actively think of singing another vowel form, as this will often create an exaggerated, or unnecessarily excessive, modification. (Although this is how vowel modification charts are generally used - that is, the student of voice is expected to sing a specific modified version of the vowel - I find that it is almost always better for a singer to aim for a certain acoustical balance and vocal freedom rather than a specific modified vowel sound.) Subtle modifications made to the vocal tract are sufficient to automatically modify the vowel, but the vocalist still thinks of and sings the original vowel. For example, when the word 'meet' is being sung, the singer doesn't actively attempt to sing the word 'mitt' instead of the original word. He or she simply adjusts the vocal tract a little, and the vowel becomes appropriately modified - and just enough to enable the singer to sing the note with good acoustical balance, ease and comfort.
When this technique works correctly, a sort of ‘hybrid vowel’ results. The original vowel will still be heard because the integrity of the vowel is still being maintained with the tongue, but it will become softened when a hint of another vowel is added as the jaw lowers. The effect is very subtle, and it takes some practice to discover what proportion of each vowel sound creates the best tone for the individual singer’s particular voice. At a certain proportion of modification, the tone will be clear and rounded, and the singer will be able to sing much more comfortably in the upper extension of the voice.
Precisely how a vowel sounds when it is modified may differ somewhat from singer to singer, and the above chart should only been studied and taken as a guideline. What vowels should be chosen to help create smooth transitions through upper-middle to upper range is dependent on the singer in question.
There must be an equalized match of timbre throughout the changing vowel spectrum; lateral vowels should not stick out as being brighter; rounded vowels must not sound darker. (Remember that lateral mouth postures uniformly raise all formants, while buccal rounding lowers them.)
If the vowel is excessively modified (too covered, narrowed or dark), it is wise to make an approach from a neighbouring lateral vowel that will heighten acoustic strength in the upper area of the spectrum.
If, on the other hand, the vowel is insufficiently modified (too open, spread and bright), excessive brilliance enters the tone, as the front vowel is conjoined with mounting pitch. In cases where the transition from the zona di passaggio (men) or middle register (women) to higher pitches produces a timbre that is too strong in upper harmonics, the positive word ‘good’ can be used. The open [ʊ] of this common word not only strengthens the lower harmonics of the spectrum, but has a positive psychological connotation as well. The singer can go directly from using this vowel to a neighbouring vowel, listening for good resonance balances among them. Other words using this same vowel sound include ‘put’, ‘book’ and ‘hood’.
Vowel modification is necessary for all voice types, especially when singing in the upper register. However, sopranos and tenors tend to have the greatest need for it because they must reconcile with the higher frequencies and intensities of the higher and louder tones that they typically sing in their repertoires. (See Formant Tuning In the Female High Range.) The gradual thinning and elongation of the vocal folds increases with ascending pitch, and this can create difficulties in the upper range of amateur and young singers. Coping with this issue demands great vocal skills and extra energy in the breath.
In the soprano voice, for example, there comes a certain point in the rising pitches when the cricothyroid muscle activity reaches its structural limit. With vocal fold elongation and the reduction in the mass of the vocal folds that regularly occurs for upper range pitch adjustments, the damping that produces the topmost pitches of the female flageolet (whistle) range takes place. As pitch mounts, the posterior portion of the vocal folds undergoes progressive damping, so that in the uppermost pitches, it is largely the anterior portion of the folds that remains in vibration. Damping can help the stress on the cricothyroid muscle because it allows only the ends of the vocal folds to vibrate with the necessary rapidity while the main body – a large segment - of the vocal folds ceases to vibrate. (High pitches of male voices also undergo degrees of damping, but they must be careful to not allow excessive damping in the higher range, as it can quickly deteriorate into pressed phonation.) Damping is not a consciously controlled laryngeal event, but correct vowel modifications will enable this process to happen naturally and automatically.