Manuel Garcia on Changing or Replacing Words when Singing:
In altering or re-arranging words, or syllables, care should be taken to retain and mark the measure or accent of a melody, and only under peculiar circumstances must this rule be infringed. The following are a few cases of this sort: -
1st. - When a singer meets with a lengthy passage of vocalisation, he may deviate from the principle, in order to obtain a favourable open vowel, a,e,o, for its execution; for example (A)
2nd. - When the number of syllables divides a passage too frequently, and has a tendency to retard the movement of the voice, it is better to perform the entire passage on a single syllable. The passage (B), furnishes an example.
3rd. - The arrangement of example (C) shows how a singer may avoid words on hight notes. Examples: - [see below.]
To avoid pronouncing syllables on high notes, recourse may be had to a lower one, on which the syllable is articulated beforehand, or else to a slur. Example: - [see below.]
The syllable thus pronounced on a low note, will enable the voice to reach the high one by means of a slight and rapid slur; and this little preparatory note, as well as the slur, must commence the time, or go to make up the full value of high note. Some consonants, m, d, d, b, &c, by the slight noise produced in their articulation, greatly assist the utterance of high notes. This noise, which precedes the emission of the sound, allows a singer to try its accuracy, and firmness of his organ, thus removing all danger of a break in the voice.
A change of vowel may, in certain syllables, be resorted to with the happiest effect. Whatever plan is adopted, these difficult passages can always be successfully sung, if, at the time of execution, the organ shall have been suitably prepared. This, in fact, is the sole object of the various methods that have been pointed out.
In the preceding rules, we have given the various modifications introduce, with the object of facilitating vocal execution. Other changes may be admitted, with the view of adding vigour to, and completing the effect of song : as, for instance, the repetition of interculation of a word or phrase, the object of which is to strengthen expression. Example: - [see below.]
Again, a singing master and pupil are at perfect liberty to add, - if the sense allow it, - one or other of the monosyllables, ah, no, si, either to increase the number of syllables, or as a substitute for others: - [see below.]
Manuel García, Garcia’s New Treatise on the Art of Singing. A Compendious Method of Instruction, with Examples and Exercises for the Cultivation of the Voice (Boston: O. Ditson, 1870).