Resonance and Vibrato in the Voice.

The purpose of this article is to explain the difference between resonance and vibrato. Many singers and teachers treat them as one and the same. As a result the voice and vocal tone suffer. A common mistake is vocal production which has too much vibrato produced by hypertension of the vocal muscles. The tone is dark and 'bleaty' and intonation is impaired. The vocalist develops problems like a sore throat and fails to sing freely. Vibrato is more noticable in the heavy, chest register. Hence pop singers will tend to use it and fail to move freely between the lighter and heavier registers. Where resonance and vibrato are balanced and the voice is working freely the benefits are a better vocal compass; proper tone matching across the significant register break (known as the 'zona intermedia') and improved vocal projection gained by use of the singer's formant. This is why singers should learn repertoire from a number of genre and not limit their studies to one genre exclusively. (A useful article about 'Vocal Ring or Singers Formant.' can be viewed at the National Centre for Voice and Speech. Be aware the the link is one way. The link is given at the end of this article.)

Resonance, in Physics, is the tendency of a system to oscillate at a greater amplitude at some frequencies than at others. These are known as the system's resonant frequencies. It does not involve a perceptible change of pitch. Vibrato is a musical effect consisting of a regular, pulsating change of pitch. It is used to add expression to vocal and instrumental music. Vibrato is typically characterised in terms of two factors: the amount of pitch variation ("extent of vibrato") and the speed with which the pitch is varied ("rate of vibrato").

Vennard, in his book 'Singing the Mechanism and the Technic', defines resonance as a large vibration produced by a small stimulus of approximately the same frequency as that of the system. Vibrato is defined as a throbbing effect due to a change of intensity, without perceptible change of pitch, in singing and in stringed and wind instrument playing. Meribeth Bunch, in her book 'Dynamics of the Singing Voice', writes 'The artistic quality of singing is frequently judged by the presence of vibrato in the sound.' Good singing has an average vibrato of from 5 to 8 pulsations per second. Less than 5 pulsations per second is referred to as a 'wobble'. More than 8 pulsations per second gives a distinct 'tremulo' or 'bleat'. The causes of wobble are frequently physical or emotional tension, fatigue or supra-laryngeal tension. The common cause of vocal bleat is excessive pressure on the vocal cords. A healthy voice will possess resonance and vibrato because these qualities give a voice character, but both must be carefully balanced.

The presence of desirable vibrato is known as 'voce chiusa' or closed voice. It produces a pleasant timbre. An unbalanced voice will either be 'voce bianco' or 'voce aperta'. 'Voce bianco' or white voice is a breathy tone. 'Voce aperta' or open voice indicates a general imbalance among resonance factors in all ranges of the voice. The higher the individual sings, the more it is evident.

There are few singing teachers who give instruction in balancing resonance, for the simple reason they themselves have never been taught how to do it. It is an aspect of vocal production which is simply left to chance. Yet good singing (that is a voice with balanced resonance) is the product of good posture,correct breathing, good muscle synergy and clear diction. There are five chambers which contribute to the production of a voice: larynx, pharynx, nose, sinuses and possibly trachea which does have a composition of hard material which may assist the production of vocal tone. Objective research has not shown that nose or sinuses play a significant role in the production of tone, but one cannot discount the efficacy of E.G. White's teaching in the first part of the twentieth century, even if his sinus-tone production technique was founded on the fallacy that the vocal cords played no appreciable role in the production of tone. Singers report a response from certain sinuses when producing tone, which are crucial in achieving 'impostazione della voce', or placement of tone. These subjective tools are significant and useful when correctly applied. The benefits may be attributed to the power of an effective metaphor well taught. The competent and experienced vocal teacher can hear the faulty tone a pupil produces and can prescribe the correct vocal or physical exercises to correct the problem. The result is progress when the pupil applies the remedy through practise.

Chest resonance and head resonance are both misnomers says Vennard in 'Singing the Mechanism and the Technic'. The former is light registration with a high formant resonance. The latter is heavy registration with low formant resonance. Curiously, the formant given by bronchotracheal resonance of E4 flat, is particularly significant because all voice can pitch it. It presents all singers with their most significant registration challenge, where both resonance and vibrato must be carefully managed and prudent teacher does not encourage the pupil to overuse the heavier register and risk vocal collapse, but helps the singer to create an overlap of light to heavy register. This is a vital part of resonance balance.

The most significant formant for a singer is that which occurs at about 2,800hz. This is known as the 'singers formant'. It is by use of this formant, which is strong in the human voice but weak in orchestral instruments, that trained singers achieve projection over the top of an orchestra. This 'ring' is an essential aspect of vocal resonance. The singer accesses this formant not by applying breath to the voice, but by correctly shaping the vocal tract. Sundburg in his article 'The Acoustics of the Singing Voice' stresses the importance of the lowered larynx found in appoggio breathing exercises, which creates a coupling of larynx to pharynx and propagates such a formant. Popular techniques do not encourage such a style of breathing. But if the singer knows how to access all qualities of voice then the choice of timbre is theirs.

Another resonance device which can be quickly learned, is the 'twang' vocal quality, produced by stiffening the collar of the larynx, by means of the aryepiglottic muscle. (This is a vocal quality which we all possess and use during the first months of our lives. It explains why babies can communicate very effectively and rarely lose their voices. The vocal stamina of the neo-natal is very impressive.) This vocal quality can be used to reinforce weaker, but more lyrical vocal tone, and is safer than prolonged 'belting'.

The Voiced Alveolar Roll and Lip Trill.

The voiced alveolar roll and the lip trill are two of the finest resonance balancing exercises I know. They encapsulate balanced myoelastic and aerodynamic action at vocal fold level, enhanced by correct acoustic matching of laryngeal, laryngo-pharyngeal and oro-pharyngeal cavities. In addition they encourage complete relaxation of the tongue at both its frontal and hyoidal extremities. This benefit is transmitted further down to the musculature of the larynx. The benefit to the singer is optimised energy and excellent projection. If the tone 'stalls' at any point it is the result of inappropriate muscular tension and/or incorrect aerodynamic action, but the exercises will naturally correct and balance both factors. Richard Miller, in his book 'The Structure of Singing', states that the voiced alveolar roll is one of the most important of all technical devices for inducing looseness of the tongue at both extremities.

All that is needed is a functional tongue point trill (ř), or a functional voiced lip trill (břřř) both actions achieve the same results: vocal release, balanced resonance and excellent awareness of the appoggio mechanism. It has opened up many a voice when applied correctly.

To begin with the singer should establish a functional lip trill or voiced alveolar roll on a single note. (Exercise 1.) Then repeat it on three notes (Exercise 2.) Finally practise a short scale of 5 notes. (Exercise 3.) Repeat the three exercises in a key a minor third higher.

More experienced singers can try the more advanced set (Exercises 4 -6).

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Copyright © 2014 Jonathan Jessop.