A discussion of the ideal "natural" vibrato, however, hinges on the perception of the vibrato as either an ornament or a continuous presence in the voice. Adopting a more "historically accurate" view would advocate the former. Baroque performers used many types of ornamental vibrato, such as the tremolo, or its heightened form, trillo, all varying in intensity according to the desired affekt*. One must assume, then, that in order to distinguish the subtle changes in intensity of the ornamental vibrato, vibrato should not be applied continuously. Anything but the type of fine, almost imperceptible vibrato that Mr. Gable advocates would obscure the ornamentation. Gable also cites Moens-Haenen's observation that continuous vibrato from instrumentalists was not acceptable during this period. (8) If, as many have argued, the Baroque instrumentalists strove to imitate the human voice, the idea of a perceptible, continuous vocal vibrato in Baroque singing becomes more and more historically "inaccurate".
Terence Kelly argues against this in his discussion of The Authenticity of Continuous Vocal Vibrato. (9) He asserts,
"Observation tells us clearly that singers can sing without vibrato. The question...is whether or not a continuous vibrato is a natural component of the voice which is trying to meet the technical and aesthetic demands of western music of the seventeenth and eighteenth centuries. I believe it is..."
Kelly explains that, as a voice develops the range and agility required of performers of Baroque music, continuous vibrato naturally emerges; he goes on to point out that not a single modern performer "who is known for his/her coloratura does not have a continuous vibrato". (10) It seems that Kelly and other continuous vibrato proponents view the "natural" vibrato in terms of physical freedom and ease of production for the singer. Rather than attempting to limit the voice in order to produce a straighter, more "natural" vibrato (in the Gable sense), this theory proposes that a singer will be able to meet the demands of difficult ornamentation and expressiveness more easily if he/she employs a continuous vibrato. In the 21st century, with 21st century voices and several other periods of repertoire to consider, this idea is anything but impractical.
*I have purposely chosen the alternative spelling- a shortening of the German Affektenlehre ("Doctrine of Affections").
8. Gable, p. 91
9. Kelly, p. 3
10. Kelly, p. 4