How to Optimise Intonation with Vowels
How to Optimise Intonation with Vowels
Contains parts from a lecture by Wolfgang Saus, 10th Stuttgarter Stimmtage, 10 – 12 October 2014.
Choral phonetics is a vocal and auditory training that allows you to control intonation and homogeneity in the choir with the timbre of the vowels.
Singers will learn to align their formants with harmonics in such a way that they fit into the musical context and match within a group of voices. Formants create an (unconsciously perceived) pitch impression that influences intonation and homogeneity. Vocal pedagogical methods of overtone singing form the basis for the training of the perception of this pitch information and for the control of formants by the form of the vocal tract.
I divide my lecture into two sections:
Distinguishing voice phonetics from speech phonetics is not new . What is new is the way in which the vowel timbre is heard and viewed as a “melody in the timbre”. When you start to hear individual overtones in vowels, vowels are heard as pairs of notes and not just as a timbre.
Experiments with amateur and professional choirs show that the sound information contained in the vowels influences the intonation even if it is not consciously perceived. The sound information is derived from the first and second formants, with the second formant having a much stronger effect.
Overtones are normally not heard for two reasons: 1) The perception of vowels is flexible with regard to formants. We hear the same vowel, even if the formants differ a fifth or more from the average. 2) The singers are not trained in the perception of overtones and therefore only listen to timbres.
Chorus singers first have to learn to consciously hear overtones in order to be able to sing their formants accurately. Afterwards they learn techniques to tune the second formant.
When choir singers synchronize their formants within a voice group, they create homogeneity. Since several positions of the formants are possible for each vowel, the conductor can emphasize those partials that fit into the musical context and at the same time stabilize other voices. The results are:
I learned to adjust the first three formants independently and accurately. The independent formant control is the basis of overtone singing, a vocal technique in which a singer apparently sings two tones at the same time by tuning two resonance frequencies to one and the same frequency and then singing a “formant melody” along the harmonic series with the resulting double resonator. For choir singers it is only necessary to control the second formant, because it conveys the predominant sound impression.
The first step to control the formants is a hearing training in order to identify the harmonics. Tongue movements are trained in a second step. The second formant is regulated by the epiglottis and the root of the tongue.
An exclusive movement of the second formant is obtained by restricting yourself to the vocal sequence I-Y-U, resting the anterior part of the tongue, jaw and lips.
Let the tongue hang out of the mouth and place it loosely on the lower lip. Then sing English YOU and French OUI in slow motion. You will hear a soft sequence of overtones that both sharpen the ear and train the motor functions for the corresponding movements of the tongue base and epiglottis.
After just one to two hours of practice, experienced singers can precisely target the second formant to half a tone.
When formants lie exactly on the frequencies of harmonics of a singing tone, the sound is full and loud, the general goal in classical singing.
As soon as the formants are being perceived and adjusted as pitches, the vowel descriptions of phonetics – closed/open, rear/front, rounded/unrounded – are no longer useful and far too imprecise for what choral phonetics requires.
In choral phonetics (generally in singing phonetics) it makes more sense to indicate the vowels as tone pairs/tripples of formants. Vocalists learn to control their vocal tract in such a way that they can change individual formants in pitch, completely different from phonetic descriptions, where two formants are mostly moved simultaneously and unconsciously. I will shortly be submitting a proposal for a singing vowel chart that describes the exact location of every vowel, regardless of language.
The possibilities to control choral vowels are limited in conventional voice training to the singers’ ability to implement the timbre by imitation, pictorial descriptions or word comparisons. In professional choirs comes the experience with which singers intuitively choose vowels that are well attuned to the musical context – usually without knowledge of the background. The better a choir masters this, the better is its sound quality.
Vowels can be nuanced up to 10 times more precisely if the formants are tuned like musical instruments. Phoneticians create formant charts for vowels by averaging the frequencies of many speakers. The comparison of different authors alone shows how tolerant our vowel hearing is to formant deviations:
The average formant frequencies found by different authors for ə deviate from each other up to a fifth. In addition, there are even larger differences between individual speakers whose values form the basis of the data.
A fifth shift of the 1st and 2nd formants is hardly a difference when speaking. However, for musicians who can tune their formants exactly, and for choir sound and intonation, a fifth is a huge difference. Theoretically there would be 7 (halftone) gradations for each of the formants of the ə nuances. In practice, however, the gradations are limited to the harmonics available. These in turn depend on the sung pitch.
The following example shows how this can look like in a choir. The word Amen is sung as a four-part D major chord.
Bass brightens up the syllable “men” a little bit with every step by placing its 2nd formant on the 8th, 9th or 10th partial (harmonic).
As soon as the bass accentuates the 10th harmonic, the perfect third (third variation, bar 6), a significant change of intonation occurs in the alto voice. It drops to the natural third (14 cents below the equal tempered thirds). The 10th harmonic, F6 sharp, in the bass voice is identical to the 4th harmonic in the alto F sharp. The alto intuitively adapts its fundamental to the perfect third in order to avoid beats (assuming chamber choir qualities). The chord results in just intonation. At the same time, soprano and alto form a perfect minor third with all harmonic and thus produce D2 as a difference tone, an octave below bass. The whole chord sounds full, room-filling and stable.
The second variant (bar 4) produces a very stable fifth. With exactly the same formant arrangement (identical pronunciation) in bass, tenor and soprano, all three voices emphasize the same overtone E6, as the 9th partial in bass, 6th partial in tenor, 3rd partial in soprano.
The syllable men is spoken with the neutral vowel schwa, ə. Depending on the fundamental tone, there are several possible timbre of the syllable in singing. Bass can sing men on D3 in such a way that either the 8th, 9th or 10th harmonic – D6, E6 or F#6 – will be amplyfied without significantly changing the vowel character.
F2 on the octave, the 8th harmonic of the fundamental note D.
F2 on the major second, 9th harmonic of the fundamental tone D.
F2 on the major third, 10th harmonic of the fundamental tone D.
In the picture the formants are recorded with vocal fry which means voiceless. The partials of the fundamental note D3 are drawn as lines. On the right you can see the position of the third “men” in the F1/F2 diagram.
In vocal-fry technique the 2nd formants are clearly audible as pitches. In the sung version, however, listeners without overtone training describe the difference rather as a slight brightening of the vowel. The formants are more difficult to hear with the harmonic as a sound source. Overtone-trained ears, on the other hand, clearly hear the partials and distinguish the vowel qualities just as differentiated as they distinguish the tones D, E and F#.
In a minor chord, on the other hand, the 10th harmonic in bass must be avoided, as otherwise the alto will not be able to keep the minor third. Minor key sounds wrong with the 10th harmonic in bass, even if all notes are sung correctly.
Special effects can be created when the 9th harmonic note (green ninth) is sung in the bass as a kind of suspended note, which relaxes into the 8th harmonic (octave) to an almost medieval calm chord.
All these effects are not consciously perceived by the listener, but they have a great influence on the impact of the music. However, in order to control these effects, the choir singers have to learn consciously to perceive the partial tone amplifications.
In practice, the whole thing quickly becomes clearer. You not only have to hear it, but also feel it physically in order to understand how choral phonetics works. It is much easier in practice than it sounds at first. The body does a lot of things on its own, because the resonance harmony is immediately expressed in relaxed singing as the ear has an archaic memory for the overtone intervals and thus for pure intonation. Both just have to be brought together first.