Vowels.
As regards vocalisation on one syllable, on long sustained notes and in the high register, the choice of vowels is a matter of some importance. The difference in the position of the mouth and lips in forming the open vowel a and the closed vowel ou is apparent to everyone. The series of vowels from the point of view of open sounds is: a, i, o, e, u. In women's voices the easiest vowel on high notes is a, for men it is o. The vowel i softens the penetrating quality of the top notes of a bass voice, and the vowel a adds to the extension of range in the very lowest compass. Lengthy florid passages are often written on the interjection ah, or simply on the vowel a. Owing to the restrictions imposed by literary and dramatic laws, the composer can only follow the above rules to a limited extent.
Examples:
Snegourotchka 293, 318-319 (cf. [Ex. 119]).
[No. 304.] Sadko 83.
Flexibility.
Voices possess the greatest amount of flexibility in their normal octave. Women's voices are more supple than men's, but in all types, the higher voice is the more agile, sopranos in women, the tenor voice in men. Although capable of performing florid and complicated figures, different varieties of phrasing and the rapid change from staccato to legato, the human voice is infinitely less flexible than a musical instrument. In passages of any rapidity, diatonic scales and arpeggios in thirds come easiest to the voice. Intervals bigger than fourths in quick succession and chromatic scales are extremely difficult. Skips of an octave or more starting from a short note should always be avoided. Preparation should precede any extremely high note either by leading up to it gradually, or by the clear leap of a fourth, fifth or octave; but sometimes the voice may attack a high note without any due preparation.
Examples:
Snegourotchka 46-48 (cf. extract, [Ex. 279])—Snegourotchka's Aria (Soprano).
" 96-97—Lell's first song (Contralto).