我本来想说些什么，但下面这篇文章says it all.  I encourage you to read it through if you are really serious about improving your singing.

Key points:

A natural vibrato is the most accurate barometer of correct vocal production. It is an even, steady tonal oscillation of the pitch center – a slight variation in pitch - and is a natural function of a well-produced vocal tone. It results from an open pharynx, or what many call the "open throat" (where the extrinsic laryngeal and pharyngeal muscles remain in a neutral “ooh” posture), along with healthy closure (adduction) of the vocal folds and good breath management.

Vibrato: What It Is and How to Develop It

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What Is Vibrato?

In vibrato, the voice is alternating subtly and very quickly between two pitches that are very close together. This periodic variation in the pitch (frequency) of a sustained musical note or tone should not exceed a semitone either way from the note itself. The effect is believed to add warmth to the voice.

Although vibrato is perceived as a pitch variant, it is discerned as a vocal timbre, or as an integral part of tone, evenly distributed over the group of notes, rather than as a pitch deviation. The pitch variance remains centered around the actual written pitch, and the listener automatically hears the average of the pitches being sung. Fully vibrant tone is squarely on pitch. When vibrato is permitted to take free-swinging pitch excursion, it actually acts as a centering intonation device. (It is more difficult to maintain exact pitch on a sustained note when singing in a “straight tone”.)

The parameters of vibrato include pitch excursion (oscillation), the temporal rate (cycles per second), and amplitude variance.

Although the purpose of vibrato is not completely understood, most voice scientists agree that vibrato enters vocal production as a relaxant principle because the body has a need for periodic muscle relaxation during heavy-duty or intense vocal activity, such as when singing sustained notes at high pitches. It is generally assumed to result from neuromuscular excitation of the laryngeal mechanism. Vibrato is the result of a balance between muscle systems in antagonistic relation to each other during phonation. When this balance occurs, the antagonistic muscle systems develop an alternating pulse that is a reflection of the continued energy level required of them to maintain equilibrium and muscular health. (Consider how muscles elsewhere in the body, such as those in our arms, begin to shake when strain or tension is prolonged. When we lift or hold a heavy object for a long period of time, we’ll often experience a periodic but constant shaking of the muscles that are being used.) In other words, the muscles of the larynx begin to pulse rhythmically in response to tension and subglottic pressure, and that produces the characteristic vibrato sound. It occurs naturally in order to protect the vocal folds.

The oscillations that occur in vibrato are the body’s reflexive response to mounting tension, and are believed to be the result of the healthy function of the vocal folds. The tension of the vocal folds is varied rhythmically, creating movement in pitch. Along with this tension change is a variation in the thickness of the folds.

Vibrato is not simply a function of the larynx. During the execution of vibrato, periodic oscillatory movements are also transferred to the tongue, epiglottis, and pharyngeal wall. This motion is a major component of the relaxation process that comes from coordinating breath energy with vocal fold responses. Even small movements of the tongue, epiglottis and pharyngeal wall may be transmitted to the external musculature of the neck. Therefore, a small amount of sympathetic vibratory action, discernible on the neck surface, is not necessarily problematic. (This vibratory movement is often more apparent in singers with thin, long necks and in those with prominent larynx’s – an “Adam’s apple” - than in those with thick, short necks or with hidden or more deeply embedded laryngeal prominences.)

Tiny movements of the tongue and jaw – not likely visible to the naked eye - can also be detected in all vibrant phonation, and may be the normal consequences of the intrinsic muscles of the larynx. The tongue floor and jaw musculature are closely related, so external movement generated by the vibrato is transferred to the body of the tongue through the tongue’s attachment to the hyoid bone, and to the submandibular muscle system. Even proper laryngeal resistance to flowing air may produce small, externally visible vibratory movements in the neck, jaw and tongue.

Despite the small oscillatory motions of intralaryngeal areas, during vibrato, the basic position of the larynx remains relatively stable (unless a singer suffers from a wobble or tremolo).

My Philosophy On Teaching Vibrato

At the risk of being labeled a bad teacher, I will confess that I am an instructor who doesn’t teach vibrato directly - not unless asked about it specifically by one of my students, and definitely not until a student has developed solid breathing technique, good tone production and at least intermediate-level vocal skills. Although I’m certainly capable of teaching the skill, I make the pedagogic decision to place little emphasis on learning it for what I believe to be very good reasons, which I will explain in the following paragraphs.

First, it may partly be a matter of personal taste, or acoustical aesthetics. Although singing with vibrato can bring vitality to the voice and stylistic variation to a song, making the voice stand out at the end of a sung phrase, I tend to like the effect only in moderation, and prefer it to be very subtle whenever it is used. All too often, and mostly by untrained or poorly trained singers, I hear an exaggerated and induced version of vibrato being used. Many singers who develop these “false vibratos” tend to overuse them, placing them on every sustained note in a song and making them extremely pronounced. (The most extreme example would be Aaron Neville, who sings with a wide-swinging vibrato on nearly every note.)

Singers who apply pronounced vibrato to every held note in order to create excitement end up producing a sound that is just as predictable and boring as that of those singers who sing every note straight (without vibrato). These singers make poor stylistic choices, overusing the pulsating or oscillatory sound because they are under the impression that vibrato, or what sounds like vibrato to them, will convince others that they are great singers. As with drum fills, guitar solos and other vocal embellishments, though, vibrato is best when it is subtle and when it contributes to the overall sound of the song, rather than detracting from it.

Second, a poor understanding of what vibrato is and how it is achieved leads many singers to vocally produce poor, often unhealthy imitations of it. Many untrained or poorly trained singers expect to feel a certain sensation or to hear a certain sound that doesn’t necessarily always accompany natural or true vibrato production. They often have these faulty ideas because they hear the type of exaggerated vocal wavering and wobbling that many contemporary singers induce in their voices and come to believe that this sound and technique is true vibrato. Acoustically and aesthetically, these overly prominent vibratos are not the best sound. They are also generally not healthy ones, either. Unfortunately, these faulty interpretations of vibrato are often reinforced by bad singing teachers who both demonstrate in their own singing and teach to their students this false vibrato quality.

Third, placing too much emphasis on developing vibrato can create stress for the student of voice. There are dangers in approaching vibrato either as a necessity or as the Holy Grail of singing. Because many teachers place so much emphasis on developing vibrato, their students often feel it imperative, and are indeed often told that a voice without vibrato is not a good one at all, and then begin placing undue pressure on themselves to achieve this goal. Anxious to be considered a skilled singer, they usually end up imitating the sound of vibrato rather than producing it naturally and correctly, often employing unhealthy methods to create the “pulsing” sound of the voice. This pressure (both internal and external) to add vibrato to the singing voice often causes the student to rush ahead of his or her voice or abilities, and I think that this practice, especially in the teacher, is highly irresponsible. The voice needs to be ready, and solid technique needs to be in place first. Otherwise, the singer can only produce a counterfeit version of vibrato, typically through unhealthy means.

Vibratory sensations in the laryngeal region should not be induced or localized. In other words, vibrato should never be faked, created or forced. Many contemporary singers fabricate theirs through poor singing technique or learn to anatomically create a false version of it through teachers with incorrect ideas and knowledge about vocal fold function and how resonance truly works.

Contemporary teachers are more likely to teach vibrato as a “trick to be learned”, (e.g., by rapidly pushing in and then releasing the upper abdomen with the hands or by quickly quivering the jaw, etc.), than are classical teachers, who understand the importance of foundation work and who are therefore more willing to be patient when developing the voice. Many contemporary teachers don't teach or model patience to their students. Instead, they guarantee rapid results with their programs, and in order to follow through with this promise of immediate vocal success, they must instruct their students to take short cuts, such as using artificial methods of making skills like vibrato happen, rather than have them first do all the tedious foundational work that would naturally produce a healthier version of vibrato. Some methods of creating a vibrato when good technique is not in place are capable of causing strain and harm to the voice – something that no good teacher should ever permit or encourage.

Those singers who fake their vibratos do so because they have poor technique. With these singers, you’ll often hear wide, slow vocal “wobbles” or overly-fast “tremolos” that sound more like pitch errors than nice effects, and you will see tension in their jaws and tongues as they are forced to move up and down rapidly with the notes. Faulty technical premises contribute to a visibly oscillating jaw and tongue. (I’m not referring to the barely detectable sympathetic movements that may result from the connection between the larynx and the tongue and jaw.) Watch Whitney Houston as she sings in the movie The Body Guard, and you’ll see a perfect example of extreme jaw movement and tension. (This is sometimes called “the Gospel Jaw”.) She doesn’t have true vibrato, achieved only by using her vocal instrument correctly. Instead, she uses other parts of her body, like her wagging jaw and tongue, to help produce that pulsating sound and look. (Whenever I watch her, I can’t help but think that she makes singing look so much more difficult and arduous than it is. If that were really the case, I imagine that there would be fewer aspiring singers in the world.) Just because a singer may have a pleasant sounding or powerful voice, it doesn't mean that they are singing correctly or healthily. Many singers sound good in spite of their technical faults, not because of them.

While training tricks like rapidly moving the stomach in and out with the hands do indeed make the voice waver, they do not provide an accurate simulation of what vibrato feels like or sounds like, nor how it is naturally produced. They provide only artificial techniques that produce artificial sounds and results. These tricks go against what is natural and efficient.

Fourth, I don’t tend to teach vibrato to my students because many of them, through the learning of excellent technique during our lessons, develop it naturally in their voices without any pressure from me. This type of vibrato sounds natural and easy, and is a healthy product of good tone production, vocal fold closure and breath management. It is true vibrato that oscillates at the ideal, steady rate, and it can be beautiful. If teachers and students focus on developing balanced resonance and a warm timbre, the voice will become vibrant, and vibrato will become a part of it. When the voice is free and the student is relaxed, vibrato will appear spontaneously. Rather than seeking to create an oscillatory sound as their prime objective, singers should instead aim for a well-balanced timbre throughout the vocal range.

I guess that my philosophy is that vibrato is not something that should have to be “added” to the singing voice – it may be either suppressed or allowed at any given point, but it is a common misconception that it needs to be added to the tone, as it exists as an important element of resonant vocal timbre. When good tone production, resonance, placement of sound, breath management, as well as relaxation, are in place, vibrato naturally results, or naturally occurs, in the singing voice. It is something that our bodies do on their own, not something that we force them to do. Singers need only develop good, solid technique. There is no trick or short cut, like rapidly pushing the upper abdomen in and out with the hands, to make true vibrato appear before the voice is ready. It will come when all the other elements of excellent singing are present. (This may become a source of intense frustration to impatient singers who want to rush ahead and acquire this sound without doing the foundational work required to encourage its presence in the singing voice. They just want to make it happen, rather than wait for it to come.)

It is possible that your voice already has vibrato, but you may not recognize it because you are accustomed to hearing the exaggerated versions of vibrato that many poorly trained recording artists use or demonstrate. As Richard Miller, a very well respected international performer, master class presenter and prolific writer on singing, would say, “Don’t assist your vibrato; it’s already there.”

Types of Vibrato

There are a few common methods for inducing vibrato, including the diaphragmatic vibrato, the vocal trill vibrato, the larynx vibrato and the “Gospel jaw”. In most cases, singers who revert to these methods, all of which create poor simulations of true vibrato, do so because of either deficiencies in their technique or the poor guidance of their voice teachers. It is my opinion that whenever vibrato can only be achieved via some kind of manipulation, the singer is lacking in technical skills and risks causing injury to the vocal instrument and developing bad vocal habits that may take years to undo.

Because these vibrato-like vocal effects are produced either by artificial methods or by unhealthy, inferior singing technique, the sound of the vibrating voice usually lacks the warm, ringing, fully resonant quality that is heard in a natural vibrato.

A diaphragmatic vibrato is characterized by diaphragmatic pulsating during a sustained tone. Airflow is modulated by periodic and rhythmic movement of the abdomen, which creates a false vibrato. Many singers develop this bad vocal habit in order to have some sort of vibrato when no healthily, technique-obtained vibrato is actually present. Some singers attempt to develop this form of vibrato and incite the pulsating of the diaphragm by either rapidly and rhythmically pushing on their abdomens below the sternum with their hands then vocalizing on a single note or panting like a dog in order to train the abdominal muscles to pulsate on their own. Panting in particular can be counterproductive, as it often leads to light-headedness (due to hyperventilation), which is the opposite of effective and controlled breathing that should be maintained during sung phonation.

To achieve the good tone that will bring out vibrato in the voice naturally, breath flow must be steady, not intermittent like the flow that is created when the abdominal area below the diaphragm is pressed in and out, even gently, from the exterior. Secondly, this type of vocalizing generally produces a tremolo effect, in which dynamic level (volume) changes while pitch remains the same, rather than true vibrato that is characterized by slight variations (or excursions) in pitch, in combination with subtle variations in tone and volume (A tremolo can sound like a permanent slow trill.) Thirdly, using a hand to make the diaphragm pulse does not assist the abdominal muscles in gaining better strength and control for singing. Although it may create muscle memory, it is likely to interfere with appoggio (breath management). Fourth, the unnatural pulsating movement of the diaphragm may make it difficult to stay on pitch because some control of the breathing mechanism is lost. Fifth, true vibrato is not achieved by making the abdomen pulsate, like that of a panting dog. The diaphragmatic vibrato is widely considered an incorrect way to go about achieving vibrato.

A diaphragmatic vibrato is difficult to reverse because the abdominal muscles memorize the pulsating sensation and develop a muscle memory. Moving the stomach in and out – tightening and releasing it repeatedly - doesn’t allow the diaphragm to move freely, and it sends an unsteady stream of air through the vocal folds that may affect all parts of singing, not just the sustained notes on which the vibrato effect is desired. However, it can be corrected through time with proper vocal exercises and a retraining of the student’s thinking on vibrato.

Some singers are instructed to awaken vibrato function by using a trill, which is an educated “yodel” at the vocal fold level that may or may not be easy for a singer to produce. Although closely related to the vibrato, a trill represents an even greater degree of laryngeal movement. As part of the inducement of pitch variation, trilling, unlike vibrato, depends on rapid oscillation of the voice box (larynx) by quick, small perpendicular motions. These movements may be observable in the front of the neck, especially if the larynx is prominent.

A vocal trill vibrato is often taught through matching pitch to the ones played on a piano. The singer moves up and down in pitch by a half step (semitone), slowly initially then increasing in speed, following the notes played on the piano. The result of this method of learning vibrato is typically a vocal wobble, as it is difficult to achieve the rapid six to eight oscillations per second rate that is ideal for vibrato. Trilling should be limited, as there may be a danger of becoming so accustomed to the physical motion of the trill that its faster rate and wider pitch excursions inadvertently intermingle with those of the singer’s normal vibrancy rate (vibrato).

The larynx (or laryngeal) vibrato is similar to the vocal trill vibrato. It involves moving the larynx up and down. Most knowledgeable instructors would agree that the larynx should remain relatively stable during singing tasks.

What I might term the “jaw vibrato” or what others might call the “Gospel jaw” describes a method of simulating vibrato by rapidly quivering the jaw and tongue. This movement creates rapid changes in tone and in vowel formation, leaving the listener with the impression that the singer is creating vibrato. However, the vibrato that is produced by moving the jaw or head is generally not very natural sounding, and the singer looks tense and silly while singing this way.

A shaking neck, together with a wagging jaw and a waving tongue are indicative of faults that originate in poor breath management or structural support. Furthermore, the tension that is created by this technique can be extreme, and can affect the health of the vocal instrument. Slight vibratory motion may be transferred from the larynx to the tongue or jaw without corrupting good timbre. Habitual shaking, however, is indicative of technical deficiencies. The teacher must differentiate between the very slight oscillatory movements of the tongue, jaw and neck that are the natural outcome of the vibrato phenomenon and the presence of undesirable tension.

Technical Faults Often Misinterpreted As Vibrato

When vocal production is not balanced, vibrato either does not occur or it occurs too fast, too slow, too narrow, or too wide. Below are a few technical faults that may disguise themselves as true vibrato production.

Caprino, which means “goat-like” or “little goat” in Italian, is a term used to describe a rapidly beating vibrato that sounds like a trill or like the bleating of a goat. It occurs when a vibrato is poorly executed, and a tremolo-like pulsation on only one note results, like the reiteration of a single pitch. It is not a sound that is produced by healthy production.

Caprino, also called trillo caprino or simply trillo, is likely caused by breath that has not found its proper point of placement and becomes dispersed. (When the breath is taught to go to the right place through technique, the voice becomes steady.) An overly fast or bleating vibrato can be caused by pressure at the root of the tongue, which may have its origin at inhalation or at the attack or onset of sound, lack of vocal fold approximation or lack of support. It may also be the result of an excessive level of energy in the high vocal range.

An overly wide and slow vibrato is typically called a vocal wobble. The wobble affects a larger variation in pitch. Its oscillation is usually somewhat slower than that of an acceptably healthy vibrato, which also effects much less pitch differentiation.

A wobble can be the result of inconsistent or inadequate breath management or “support” (e.g., too little breath energy), a lack of focus in the tone (distorted acoustics with improper or imbalanced tone), a lack of proper (firm) adduction (closure) of the vocal folds, singing with too much "thick vocal cord mass", dragging too much chest voice or "heavy mechanism" too high - thus the entire voice suffers from overblown or over-weighted production - or a shaking diaphragm. Singers who use an extremely lowered laryngeal position will eventually sing with a slow, wide vibrato - the stereotypical operatic sound. Over-weighted voice production (trying to sing too “big” or carrying the heavier, “lower mechanism” too high in the voice) can slow down both the temporal (per-second) and pitch excursion rates of the vibrato cycle, and the accumulating air pressure can make the voice sound tremulous. This also causes intonation problems, with the pitch going flat and a lack of upper overtones.

Short energetic agility exercises that require flexibility and greater freedom may help to speed up the oscillatory rate. Each of these short patterns should be concluded with a sustained note, retaining the same energy. Excitation of the fast-moving, short pattern will induce vibrancy on the longer note as well.

A tremolo is characterized by an overly fast oscillatory rate. This tremulous effect can be produced by either the rapid repetition of a single note or the rapid alternation of two tones, although the term is generally used to refer to a pulsation that affects volume only. It often comes about when singers attempt to assist the vibrato by increasing glottal pressure (using too much breath energy), thus tying too hard to “support the tone”. A tremolo can be caused by a pressure built up at the root of the tongue. This pressure can have its origin at inhalation or the beginning of sound production. It can also be caused by a lack of vocal cord approximation.

Singing in a straight tone may help to correct the problem of a persistent tremolo in the voice. Thinking about removing some of the vibrato can help to reduce the pressure at the glottis, and can result in a slower, more acceptable vibrancy rate.

Any extreme form of vocal production will eventually produce a problematic vibrato. When vocal production is not balanced (or “free”), vibrato does not occur, or it occurs in one of its aberrations: too fast (bleating), too slow (wobble), too narrow, or too wide. It is not induced by the singer through any conscious method, but it may be suppressed through conscious control.

How Is Vibrato Naturally Produced?

A natural vibrato is the most accurate barometer of correct vocal production. It is an even, steady tonal oscillation of the pitch center – a slight variation in pitch - and is a natural function of a well-produced vocal tone. It results from an open pharynx, or what many call the "open throat" (where the extrinsic laryngeal and pharyngeal muscles remain in a neutral “ooh” posture), along with healthy closure (adduction) of the vocal folds and good breath management.

Natural vibrato is the result of healthy, coordinated singing, not manipulation. When optimal support, airflow, tone (resonance) and relaxation are in balance, the vibrato will take care of itself. I understand that it may disappoint many aspiring singers to learn that vibrato will appear naturally only when the voice is ready – when the singer has developed good technique. It requires patience and discipline, but allowing vibrato to be the natural, healthy byproduct of good singing technique is well worth the wait on so many levels. We don’t need to create our voices or add anything to them, including vibrato.

A natural vibrato will be neither too wide nor too narrow in its pitch variance and will, ideally, have an oscillatory rate of approximately six to eight oscillations per second.

In addition to developing an ideal vibrancy per-second rate, another key factor in attaining a healthy sound is to be sure that the vibrato is vibrating at an even rate. A consistent vibrato can be achieved only when airflow is evenly regulated and vocal fold closure is sufficient. An even vibrato rate is evidence of balanced resonance. Because a good vibrato vibrates at an even rate, it is important that a singer hoping to learn vibrato first learn to breathe well. The singer needs to maintain good posture for support, with the back, neck and head in alignment. Subglottic pressure can be regulated by the support system, which involves the abdominal muscles, lower lumbar/upper gludial muscles, intercostals muscles and pectoral muscles.

As with many problems of the singing voice, faulty breath management may be the cause of non-vibrancy. An uneven vibrato rate may be caused by sudden changes in the sub-glottic breath pressure created by poor breath support. These sudden changes in the air pressure are the result of uneven "body resistance" from the singing support system. The vocal folds then begin to separate and vibrate unhealthily. The result is an uneven vibrato sometimes accompanied by pitch problems.

Richard Miller believes that vibrancy can be aided or induced and its cycles-per-second rate steadied by trying this exercise: Retain the inhalatory abdominal wall position throughout a vigorous glissando up and down while quivering your voice like a ghost. (It seems silly, I know.) There may be some almost imperceptible pulsing in the abdomen while at the same time appoggio contact is retained. These maneuvers may help to induce vibrato in a healthy manner and steady its cycle-per-second rate.

Tips For Developing Vibrato

First, vibrato generally goes in tandem with vocal development. With better technique, which includes tone and breath support, vibrato is likely to appear naturally, with little effort on your part. Therefore, it is imperative that you focus on developing solid vocal technique if you wish for vibrato to become a part of your vocal timbre.

Second, vibrato occurs more readily in voices with clearer, more efficient tone. Good vocal technique produces clear, resonant, vibrant tone, so spend as much time as you need on perfecting your tone. Ensure that you have adequate vocal fold closure so that your tone is not breathy. Vibrato is not likely to be present while there is breathiness, (or “fuzziness”) in the tone. (Look for an in-depth article on tone production on this site in the near future.)

Third, vibrato is best realized as a function of relaxation – but not too much relaxation. With adequate vocal development and clarity, relaxing your vocal apparatus is sufficient to incite or allow vibrato.

Finally, have patience. Work on your technique, and vibrato will appear when your voice is ready. (Again, this is likely not what you want to hear, but it is true.) It won't come naturally and healthily if you do not have good technique. First things first. Aim for good, clear, fully resonant tone, with proper adduction (closure) of the vocal folds, and a steady, controlled stream of airflow with the optimal level of breath energy, in order to produce the vibrancy that leads to a naturally occurring vibrato.

Your main goal should be to develop good timbre (vocal quality) throughout your entire range, not to produce an oscillatory sound. Don't place too much pressure on yourself, and don’t be tempted to rush ahead of your voice’s development, as this will lead to desperation and poor choices, like trying to induce vibrato artificially. Don’t be discouraged if vibrato doesn’t appear in your voice right away, or within the time frame that you have deemed to be acceptable.

Also keep in mind that many of the singers that you hear today have really wide-swinging vibratos that are exaggerated and poorly executed. Don't expect your vibrato to be this pronounced. It is possible that you may already be able to sing with natural vibrato, but you don't recognize it because you are expecting the pitch excursions and oscillations to be more dramatic than they naturally are, like the ones that are modeled by many popular singers.

Can the Voice Be Vibrant Without Vibrato?

Contrary to the opinions of many instructors, and even many who are highly respected master teachers, I don’t believe that vibrato is essential to good tone or singing, at least not the type of feigned, overly apparent vibrato that is generally heard in contemporary singers, but also in many opera singers. A singer can sing with full vibrancy in the absence of a noticeable or exaggerated vibrato, with the fundamental and its overtones fully present. (Vibrato can also be present in the singing voice without it being overly prominent.)

There are many instructors who reject the idea of so-called “straight singing”, calling it an unhealthy and inferior style or claiming that singers who sing without very present vibrato have inferior technique and imbalanced vocal production. They argue that suppressing vibrato through constrictive controls affects the vibrancy that is essential to the professional chiaroscuro timbre by creating an imbalance among the fundamental and its overtones, and thus reducing voice quality to one uniform color. In other words, straight singing is thought to strip the voice of its timbre and centered intonation.

Even in so-called straight singing, though, a singer can access all of the richness and vibrancy of the voice, as can be heard during parts of a sung phrase without sustained notes. The vibrato that is naturally occurring is not suppressed. Rather, it is simply not forced to stand out or to be overly prominent. For many styles of music, vibrato can be reduced to the point where it is almost imperceptible, rather than eliminated altogether, and a singer will maintain a healthy voice with resonance and power.

I believe that many of these teachers are confusing and mislabeling a “straight singing” effect or style, which can be fully resonant and vibrant in the absence of a noticeable or free-swinging vibrato, with the “pure-tone” aesthetic of some choral traditions. (This may simply be an argument of semantics.) Proponents of the pure-tone sound do indeed strive to have all the voices in their choirs sound alike, and therefore have their members alter vowel formation with mouth shaping techniques in order to strip the individual voices of their unique timbres (colours). This sound is not ideal in professional solo singing, as the timbre of the voice will sound thin, held and lifeless. Singing this way can be damaging to the singing voice over time, as it places stress on the vocal folds. Good choral vocal blend can be achieved through healthier means, (e.g., vowel and acoustical alignment) rather than squeezing the singing voice into a so-called straight tone.

There are situations in which vibrato is an undesirable effect. In choral work, vibrancy rates among individual choir members may differ either slightly or enormously, and vibratos that aren’t synchronized can destroy the quality of a soft, unison passage. Wide-swinging vibratos that aren’t squarely on pitch in one singer can throw off the pitch of other singers standing next to them in the group. Most choir directors make the decision to have everyone sing in a “straight tone” to avoid such inconsistencies in the overall sound of the choir. A straight tone can help singers in a large group blend more easily with each other. Therefore, tempering how much vibrato a singer uses or has, if any at all, is a valuable skill in an ensemble situation.

Another situation in which use of vibrato is inefficient or impractical is in the singing of either very quick passages or melismatic passages. (A melisma is a string of notes that are sung on a single syllable, or the technique of slurring a sound over several notes, creating greater fluidity in a song.) A singer’s vibrato must be eliminated or suppressed during the singing of swift moving melisma because there is no time for each note of the passage to accommodate the excursions of the vibrato rate.