There is a trend in modern classical singing for an approach which I call Omnivowel™. I’m trademarking it now because I’m sure it will show up over time, and you’ll have heard it here first.
Omnivowel singing is usually the result of pedagogies that rely heavily on vowel modification in the passaggio and above. The tone is heavily modified to an ‘uh’ vowel with indistinguishable vowel clarity between phonemes. A quick example of this would be singing ‘Caro mio ben’ as “Cuh-ruh miuh buhn”.
Omnivowel is primarily present in the male classical singing voice and brings focus to the concept of ACTIVE and PASSIVE vowel modification. According to Kenneth Bozeman in his book Practical Vocal Acoustics he describes it as follows:
“In scalar passages it is most elegant to accomplish a smooth, gradual turning across the span of a couple of pitches. However, the turn can be exaggerated in any voice by active vowel modification: choosing a more open timbre just below the turn, then creating a deliberate, heavier cover at the turn…Such a move will precipitate a more dramatic, deliberate turn, which – if not too exaggerated – might be effective for strong expressive effect, but if used at all, should be reserved for special circumstances.”
The banner of active vowel modification was carried in the 20th Century by Richard Miller in his books and writings. For Miller, beginning vowel modification in the passaggio aims to unify the voice in timbre. All vowels are gradually migrated to ‘uh’ in an attempt to unify the timbre of the voice. In an ideal world, this system also maintains an open throat through the gradual opening of the mouth as well as increased ‘breath support’. The modification of vowels for Miller is always in conjunction with an increase in ‘support’ or ‘breath energy’.
In terms of registration, Miller’s theory may indeed encourage greater participation of the head voice by moving away from ‘chestier’ ‘open’ vowels. The theory also works well in singers with a developed head register, but less so with singers without a functional head voice.
The problem with active vowel modification from a functional perspective is this: if there is only one register being used, then modification is the ONLY way for a singer to gain any kind of top voice. The voice never leaves its chest dominance in the passaggio, and modification allows the singer more top notes. However, the tones are usually loud, covered, and lack any dynamic contrast. Messa di voce on these tones is impossible, as there is no balance between the arytenoid and cricothyroid muscle systems.
For Manuel Garcia, vowel modification was a ‘convenient resource’, but not the basis for a technique. In Lamperti’s treatise, he insists that the ‘open’ quality of the voice should be preserved no matter where in the range and care should be taken no to modify the ‘ah’ vowel to the ‘oh’ vowel. Many writings from historical writers insist on purity of vowel as the hallmark of great singing. Klaus Georg had the following to say on the subject:
In his book Training Tenor Voices, for example, Miller makes absolutely no mention of messa di voce. This is because it cannot be taught through vowel modification and support alone, especially in the male voice. The true scala filata can only be achieved by a registrationally perfectly balanced voice. Comments on messa di voce in his book Training Soprano Voices are limited to definition and exercises, not on how to achieve the effect in the first place. By contrast, Garcia gives precise and detailed registrational instructions on how to achieve the messa di voce (Garcia 1984, 133-136).
Miller, on the other hand, is much more detailed about breathing. While posture plays an important role in his ideas about breathing, he quite specifically mentions the balance of different abdominal and intercostal muscles with respect to breathing. His ideas about breathing are also grounded in the Italian idea of appoggio.
By controlling vowels, a teacher attempts to fix the symptoms of improper register balance. This is also the case when direct attempts are made to affect laryngeal position, tongue position, vocal timbre, mouth position, and various forms of constriction. Registrational manipulation goes to the cause instead. With the possible exception of breath control, all other technical vocal problems are a result of improper register coordination.