The issue of vibrato in a singing tone causes many problems for singers. Although all singers are concerned with their vibratos, choral singing often gives rise to vibrato problems, and many of these problems occur in choral singing. Many choral directors want that elusive thing, “blend,” and worry that, when their singers give them a tone with vibrato, the blend will be ruined. Clearly, they equate vibrato with tremolo or wobble. In so doing, they are blaming the wrong thing. A vibratoless tone resembles a boy soprano’s tone, where absence of vibrato is natural. Singers are confused when someone tells them to take the vibrato “out.” This is because they do not believe that they are “putting” vibrato “in.” It is a natural component of adult singing.

            Let us use the choral director’s reasoning and attitudes in order to clarify our own. One wonders whether choral directors have ever noticed that orchestral conductors never ask their instrumentalists to “synchronize their vibratos?” Observing, one can see that the string players are actually moving their hands in various rhythms to achieve their vibratos. The movements are far from uniform among the players, although the resulting tone is in accordance. Nor do orchestral conductors consider whether or not there should be vibrato in their instrumentalists’ tone. It is viewed as a necessary component of a beautiful tone. So should it be with a singing tone.

            Many choral directors believe that a soft dynamic level will obliterate the vibrato and deliver “blend.” In this belief they are wrong. Vibrato will still be there in pianissimo, just not as audible. More importantly, expressive possibilities are severely limited when only soft singing is permitted, and vocal fatigue is a sure result. Dale Moore, noted pedagogue, has this to say: “I would rather have a soprano of potentially operatic caliber serving as part of a cheerleading squad than have her singing in a group where the tonal ideal for a soprano is the sound of a tired English choirboy.” Paul Kiesgen, celebrated teacher of voice and vocal pedagogy, echoes Moore: “Loud singing with inadequate vocal technique can be harmful....Poorly produced soft singing, however, can be equally harmful....For most voice students, soft singing is the last skill mastered and one of the most difficult to acquire.”

          Often choir directors justify their dislike of vibrato in a tone by citing a belief that singers of early music never used it. Before we accept the premise that singers in Renaissance and other early music styles used no vibrato we must ask several salient questions:

            1. Do contemporary writers from these two periods accurately describe in unmistakable terms the sounds they admired and those they disliked? Bear in mind that there are no recordings from which we could draw our own conclusions.

            2. Do the writers of the period clearly indicate that there was or was not vibrato in the vocal tone? Or whether some singers used it and others did not? Do they report whether some singers may have used it part of the time for specific music and eschewed it in other music? Are we in fact sure of the meanings of the descriptive words used by period writers on music? Do we now understand what was meant by the terms they used at that time? (Even present-day voice teachers have considerable difficulty agreeing on exactly what constitutes a wobble, or tremolo, or even the desirable degree of vibrato.) Do we really know exactly what Tosi meant by his treatise of 1723, often quoted by both sides of the vibrato argument?

            3. What does the music itself really tell us? We know that the use of the voice changed significantly in Rossini’s day after the tenor Dupré demonstrated the possibility of the high C in full voice rather than falsetto. Was there a significant change at some earlier point between the early music we are discussing and that of, say, the Baroque?

            4. Does the range used preclude the use of any particular type of tone? How about the tessitura of solo parts and the tessitura of ensemble parts? It is possible that some of the dissonances used must have been sung without vibrato for the sake of clarity and accuracy. Was a distinction made between the tone adopted by soloists and by ensemble singers?

            5. Do we have any reliable information on the vocal longevity of singers of that period? Did they go on singing well into their later years as some of our recent and even present singers do? Were there in fact professional singers in the current sense at all?

            All of the above questions (extracted from a Statement issued by the American Academy of Teachers of Singing, “Early Music and the Absence of Vibrato”) seem relevant to the subject of singing early music and the possible vocal abuse in relation to singing early music. Choir directors should know that, across the profession, voice teachers are very concerned about the vocal debilitation that occurs in their students who sing nothing but early music in groups that shun vibrato.

            Former Indiana University pedagogue and vocal researcher, and a great singer himself, Ralph Appelman, wrote, “Correctly produced, the vibrato is a vocal ornament that is directly related to the sensation of support. It is physiologically controlled by the muscles of respiration and is thereby, basically a respiratory function assisted by coordinated laryngeal controls.”¹

            The assurance with which Appelman makes this statement should not cause us to ignore the complexity of the task facing the singer who is attempting to keep an optimal vibrato rate through the vicissitudes of :

                        singing in many different musical styles:

                                    (early music, mainstream, bel canto, jazz, Middle Eastern, etc.),

                        changing dynamic levels, crescendos and decrescendos, sustained

                                    and non-sustained utterances (trills, staccato, marcato,

                                    martellato, etc.),

                        fluctuating vowel and consonant demands of different languages,

                        activating glottal onsets, stresses, and unvoicings in languages not

                                    their own,

                        achieving their musical intentions or those of their conductor,

                        executing extreme pitches, both high and low.

These are not simplistic tasks and they are not made easier when the singer does them as part of a group in a chorus situation.

            Each of the tasks listed above influence the rate and extent of the vibrato. Each of the tasks listed above are made easier by the maintenance of the appoggio, which produces vocal stability.

Some Science Background on Vibrato, Tremolo, and Wobble

            If you are not interested in the scientific studies of vibrato, feel free to skip this section, although reading it will undoubtedly clarify your thinking on the subject.

            As long ago as the 1930s, Carl E. Seashore initiated a study of the vibrato. Until only very recently when the issue was raised again, by Ingo R. Titze among others—without conclusions as yet—the results have stood as a hallmark. Seashore’s definition of a vibrato is the traditionally accepted one: “A good vibrato is a pulsation of pitch, usually accompanied by synchronous pulsations of loudness and timbre, of such extent and rate as to give a pleasing flexibility, tenderness, and richness to the tone.” ²Several important points were revealed in the Seashore study, among which were these, roughly extracted from that study:³

1. The vibrato is a fundamental attribute of the artistically effective singing voice.

2. With the exception of trills, and an occasional note, every tone of every artist registers vibrato, whether long or short, gliding or steady, high or low, pianissimo or fortissimo. The upper and lower limits of each vibrato pulse...are always present.

3. Most singers cannot sing a tone that would have any semblance of desirability without using the vibrato.⁴

4. It is this fact--that the vibrato is not heard even by the best musician as it really is--that lies at the bottom of the confusion which has prevailed on this subject.

5. The impression that a vibrato disappears in pianissimo is false. When a vibrato is not detected in pianissimo tones, it is a fault in the ear of the listener. The vibrato is actually present in production.

6. Both the extents and rates of the vibratos of excellent singers are in a continual state of flux.

7. The whole problem of the prominence of the vibrato in a voice revolves around auditory fusion. Probably the fusion of the slower vibrato rates is not as perfect as the fusion of the faster. At the slower rate...the vibrato is less of a unity since it is completely broken...Too fast a rate, such as in a flutter, also attracts attention more than the artistic vibrato rates.

8. Although the vibrato consists of a frequency pulsation in the sound wave, it has only one salient pitch in perception. This perceived pitch is approximately midway between the extremes. There are individual differences. The vibrato that one person hears as in tune may be appear to be out of tune to another person, pitch discrimination being equal.

9. Those who are most critical of the vibrato are generally those with very sharp ears for pitch discrimination. To those, a vibrato that is too slow or too wide is undesirable because the two notes cannot blend into one.

         Dr. Friedrich Brodnitz, a leading New York otolaryngologist of the fifties, stated: “A well-trained voice exhibits always a certain amount of vibrato that gives changes, both in pitch and volume. By vibrato we understand small rhythmical changes in pitch and volume. These oscillations are more noticeable in forte than in piano....If the wavering becomes excessive—up to twelve times per second—it is called tremolo.”⁵

         Later scientific authorities also do not disagree with Seashore’s earlier findings: Vennard (1971), Large (1971), Shipp and Izdebski (1975), Shipp, Leandersen, and Sundberg (1981), and Hirano (1985) all consider a vibrato of from five to eight regular pulsations per second to be that of a good singer. They are in agreement that pulsations slower than that (called a wobble) are picked up by the human ear as separate pitches and unpleasant, and that a rate of more than eight pulsations per second is too fast, producing an equally unpleasant sound (called a bleat or tremolo).

            The ordinary and extraordinary tasks for which a singer is often responsible present a variety of problems that impinge upon the desired stability of the vibrato.

1. The extent of the vibrato decreases when rapid pitch changes take
place. If the vibrato frequency could be matched to the rate of
pitch change in an agility passage, this difficulty could be avoided,
but the singer must choose his/her tempo with that principle in mind.

2. Jazz singers commonly change from straight tones to a vibrato tone by
altering vibrato extent. See the paragraphs following the science section
below for definitions of rate and extent.

3. Sustained, slow moving music accepts more vibrato than fast-moving music.

4. Middle Eastern music asks that the vibrato extent be reduced even
further in order to distinguish between melody and vibrato.

5. Whatever we perceive, neither the straight tone nor the vibrato tone is
rock-steady, although they are more steady than a tremolo.

6. When pitches vary, intensity and timbre fluctuate greatly.

7. Classical Western singing styles have not always asked for the same
type of vibrato; in fact, they have changed in the last century.
In Carl Seashore's day  (the 30s) faster vibratos were common (6.0-7.0);
Caruso's vibrato was near 7.0, whereas Luciano Pavarotti's
average frequency is near 5.5 Hz.

8. Some shapes of the vocal tract--consonants--may affect phonation to such
a degree that it is difficult to keep a stable phonation. Thus one could
expect disruptions in vibrato during a great deal of changing articulation.

9. Since vowels tend to have intrinsic pitch because of the tongue and hyoid bone
height, rapid changes of vowels may cause some vibrato frequency
instability, even when the singer's intent is to keep the frequency steady.

          Recognizing the facts listed above, the question still remains: What is an acceptable frequency and extent for a vibrato? A simple answer is 4.5 - 6.5 Hz in frequency and 0 - + or - 3 % (+ or - .05 semitone) in extent. This answer demands a great deal of explanation. Vibrato extent increases with a crescendo. Vibrato frequency increases with pitch and with level of excitement. Therefore, a wobble is the result of a lack of excitement, poor muscle tone, or fatigue. (This suggests again that physical fitness and good vocal conditioning is necessary.)

          Vocal researcher Ingo Titze reminds us that “a vocal vibrato may be described as a fluctuation in fundamental frequency and amplitude....The vibrato is itself a pattern, rather than a deviation from a pattern [my emphasis].”⁶

          When, as Ralph Appelman states, “minute alterations of body pressure...are reflected in undulations to the breath column,” a vibrato is produced. “The singer is attempting to control the pitch by keeping the mass, length and tension of the vocal cords constant.”⁷ Therefore, the singer who does not sing with proper support cannot control the vibrato rate. The appoggio is again a primary answer, this time to vibrato ills.

Rate and Extent and their Effect upon Vibrato Difficulties

            There is virtually no disagreement among vocal pedagogues and voice scientists regarding the cause of vibrato difficulties: the two main causes are: (1) excessive tension in the laryngeal mechanism and (2) unbalanced breath support. The answer to the problem of tension lies mostly in relaxation techniques. The solution to unbalanced breath support is the appoggio. (See the articles "Breath Management" and "Update on Breathing" for the method of finding and maintaining the appoggio.) Since proper vowel modification results in less laryngeal tension, it also plays a related part in vibrato stability.

            Vibrato faults, which are not mutually exclusive, can be categorized like this: defects of rate, defects of extent, and defects of breath energy.

• Rates can be too fast or too slow.
  
            Rates faster than five to seven times per second are generally judged as unacceptable, as are rates slower than five times per second. When a muscle is tensed for too long and not allowed to relax, it will begin to quiver and eventually develop an uncontrolled tremor in the tongue, jaw, larynx, abdominal muscles, and rib and chest muscles. If the quiver is fast, the vibrato will be fast, nervous, and insecure. Quivering in the larger muscles of the body takes longer to begin to shake. Therefore the vibrato will come in slow wave--a wobble-- producing insecurity in the pitch and tending toward too loud. Slow vibratos can also be instigated by trying to produce a bigger sound than the voice is sized for, or by supplying too little support to a genuinely large voice. A bleat is the result of the larynx alternately resisting and releasing the excessive breath pressure. Forcing the chin down against the larynx will make the vibrato change both rate and extent erratically and irregularly.
  


• The average acceptable vibrato displays an extent of one quarter tone above and below the desired pitch.
  
            When the extent approaches a whole step or less than a quarter tone, the perception is one of an unacceptable width or a perilously straight tone. The aberrations rising from unbalanced breath energy are probably most objectionable.The singer should be checking for both excessive tension and unbalanced support. The location of the various quivers is a clue. Audible but not visible vibrato faults indicate that the cause is in the larynx or the support mechanism. Most authorities would vote for the breath support as the likely culprit. Teaching yourself to maintain an appoggio for inhaling and for singing is a must.
  
• The bleat has two causes.
  
            First, the tension in the abdominal muscles must be reduced. Second, the cords must be trained to stay in continuous phonation. This can be effected by using legato exercises while not pushing the breath. The cause of a unwanted straight tone is tension in the larynx or the tonal model of the singer. Perhaps the singer was told at some time that his/her tone was too shaky. Maintaining the appoggio should alleviate the problem. The slow, wide vibrato--a wobble--is unfortunately prevalent among choral singers. The culprit, in addition to the absence of an appoggio, is lack of physical and vocal exercise. Bending and stretching exercises are recommended during the warming-up period and in private. This will be a help to older singers.

                    Balanced support (the appoggio) and released tension will be major factors in alleviating your vibrato problems.

Why the Appoggio will Alleviate an Objectionable Vibrato

          Three eminent vocal pedagogues/vocal researchers supply the reason for depending upon the appoggio for the greatest help with objectionable vibrato problems:

                 “The acoustical properties of vibrato are obviously inter-

dependent with aerodynamic events and muscle activities

related to phonation.”⁸

                   “Support of tone is dependent upon maintenance of subglottal

pressure. This is done by maintaining balance and position of

the rib cage, which allows abdominals and diaphragm to

function efficiently. Inexperienced singers allow the rib cage

to be drawn down by increasing expiratory effort. When the

rib cage is high, continuing thrust from the abdominals gives

a steady tone.” ⁹

                   “A perfectly controlled vibrato rate is the result of a balanced

musculature conceptually energized by the muscles of respir-

ation (rib-raisers holding against the rib-depressors) assisted

by specific laryngeal control, i.e., control of length, tension,

and mass of the vocal folds.”¹⁰

         Vowel modification also contributes to solving the vibrato-tremolo-bleat-wobble problem. Since Seashore’s day, it has been noted that in good singing the center of the vowel is the center of the pitch. When there is no warring between the pitch frequency and the vowel frequency (a correctly modified vowel), there will be an artistic, highly acceptable vibrato.

         Nevertheless, the best aid in combating a troublesome vibrato remains the constant maintenance of a proper appoggio: that is to say, high sternum, extended ribs. See the article "Update on Breath Management".

ENDNOTES 

1. D. Ralph Appelman. The Science of Vocal Pedagogy. Bloomington: Indiana University Press, 1967.

2. Carl Seashore. Psychology of Music. New York: McGraw-Hill, 1938.

3. Ibid.

4. Milton Metfessel. “The Vibrato in Artistic Voices,” in The University of Iowa Studies in the Psychology of Music. Iowa City: University of Iowa Press, 1932.

5. Friedrich S. Brodnitz, M.D. Keep Your Voice Healthy. New York: Harper and Row, 1953.

6. Ingo R. Titze. Principles of Voice Production. Englewood Cliffs: Prentice-Hall, 1994.

7. Appelman, 1967.

8. John Large and Shigenobu Iwata. “The Significance of Air Flow Modulations in Vocal Vibrato,” The NATS Bulletin, February/March 1976. 

9. Maribeth Bunch. Dynamics of the Singing Voice, 2^nd Ed. Vienna: Springer-Verlag, 1993.

10. Appelman, 1967.