Formant Frequency Shifts for Classical and Theater Belt Vowel Modification
Titze, Ingo, Journal of Singing
(ProQuest: ... denotes non-USASCII text omitted.)
AN INFORMAL STUDY was conducted as a classroom exercise at the 2010 Summer Vocology Institute in Salt Lake City. Eleven students, each with five years or more of classical voice training, had been instructed in belt technique by a faculty member of the Brigham Young University music theater and dance department. A sequence of five speech vowels, phonetically written as /i/-/e/-/a/-/o/-/u/, was produced with the vocal fry (pulse register) technique to provide formant frequencies on a spectrum display (Voce Vista"). Four formant frequencies were measured for each vowel in the sequence, and entire sequence was repeated three times to determine the reliability of the measures.
The singers then were asked to modify the vowels to approximate an inverted megaphone mouth shape (wide in the back of the mouth and pharynx with only a moderate lip opening, as often taught in classical singing in the G^sub 4^-D^sub 5^ pitch range). The modification resulted in an approximate phonetic description of /I/-/ε/-/Λ/-/.../U/ for the vowels. Three repetitions of each sequence were produced. A megaphone mouth shape (wide open at the lips with no attempt to widen the back of the mouth or pharynx) was then produced by each singer. This modification is typical for belt production around G^sub 4^-D^sub 5^. The phonetic description was /i/-/e/-/æ/-/a/-/.../, although the /i/ was not deemed a belt vowel by the instructor. There was little lip rounding for the /.../, the belt modification for an /u/.
Figure 1 shows the first formant frequency (F1) across vowels for a male singer. The speech vowels showed the greatest F1 range, from around C^sub 4^ for /i/ to around E^sub 5^ for /α/ and back to E^sub 4^ for /u/. The classical singing first formant frequencies had a much smaller variation across vowels. In fact, except for the /α/ vowel, they all clustered around C^sub 5^, suggesting that the modification is used to strengthen the fundamental (first harmonic) frequency of the source for notes in the G^sub 4^-C^sub 5^ range. These are high notes for males and mid-range notes for females.
For the belt vowels, mainly /æ/,/a/, and a very bright /.../, the first formant frequency approached C^sub 6^, suggesting that the second harmonic (2F0) from the source can be reinforced for notes in the G^sub 4^-C^sub 5^ range. In other words, F1 is raised nearly by an octave to resonate the second harmonic instead of the fundamental. …