Voice Research and Technology ASSOCIATE EDITOR: Ingo Titze Vowel Modification Revisited cal differences, formant frequen- first formant and raises the sec- cies are unique to each individual. ond formant, while backing and 2. The amount of modification lowering the tongue raises the first needed varies with the size of the formant and lowers the second for- voice, the "weight" of the voice, mant; (d) opening the jaw raises the duration of the note being con- the first formant and lowers the sidered, the dynamic level, and second formant. how the note in question is ap- Other information now needs to be proached. Sensitive singers report integrated into pedagogical approaches. that the amount of modification Three areas of continuing study have they need may vary daily and also particular significance for singing during the day, depending on how teachers. much they have warmed up. The effect of subgiottal resonances 3. Vowel formants are frequency upon vocal fold vibration. Just as the John Nix bands, not one specific pitch. vocal tract above the vocal folds has 4. Precise tuning of each note in a different formants, so too does the In the last forty years, many voice piece is not very practical nor is it subglottal airway. The primary dif- pedagogy authors have written about acoustically beneficial. During a ference is that vocal tract resonances the need for appropriate vowel mod- rapid passage, a singer may not can be altered consciously by moving ification. Modification involves shad- have enough time to adjust for opti- the tongue, lips, jaw, palate, and lar- ing vowels with respect to the location mal resonance on each vowel on ynx, while the subglottal airway of vowel formants, so that the sung each note; moving on to the next remains basically the same for all vow- pitch or one of its harmonics receives note in the passage smoothly is a els. So while the vocal tract formants an acoustical boost by being near a greater priority than exact tuning vary from vowel to vowel, the sub- formant. The goals of modification of each tone. glottal formants are relatively "fixed," include a unified quality throughout S. Males and females "tune" differ- with only a slight amount of variation the entire range, smoother transitions ently. In general, males seek to possible due to changes in laryngeal between registers, enhanced dynamic match harmonics above the fun- height. The relationship between the range and control, and improved intel- damental to a formant, while sung pitch and the effect of these sub- ligibility. Elite singers, whether they females, especially in the upper glottal formants on vocal fold vibra- consciously recognize they are mod- voice, tend to reinforce the fun- tion should be incorporated into ifying vowels or not, become experts damental itself by matching it to pedagogical approaches (Figure 3). at making subtle changes in vowels the first or lowest formant (Figures The implication of subglottal reso- as they sing, or they do not have con- 1 and 2). nances for singers is that at some sistent careers. Modification concepts 6. Several general "rules" for modi- pitches, particularly around D3 and that have been widely accepted are fying vowels exist (as summarized D4, pressures due to subglottal reso- summarized as follows: by Titze): (a) formant frequencies nances increase the amplitude of the 1. Although there is a strong corre- lower uniformly by lengthening vibration of the vocal folds, while at lation between voice classification the vocal tract (either by lowering other pitches, especially around G and formant frequencies, due to the larynx or protruding the lips and C5, subglottal resonance factors subtle articulation and anatomi- or some combination of both); (b) decrease the amplitude of vocal fold formant frequencies are lowered vibration. Titze suggests that this •Journal of Singing, November/December 2004 Volume 61, No. 2, pp. 173-176 uniformly by lip rounding and change in vocal fold vibration can be Copyright 2004 raised by lip spreading; (c) fronting controlled by adjusting vocal fold National Association of Teachers of Singing and arching the tongue lowers the adduction slightly. When subglottal NOVEMBER/DECEMBER 2004 173 John Nix driving pressures substantially increase vocal fold vibration amplitude, a slight increase in abduction may be war- ranted to prevent overdriving the sys- tem; when subglottal driving pressures substantially decrease vibration ampli- tude, a slight increase in adduction maybe helpful. By doing so, the singer may avoid large changes in intensity from one pitch area to another. Male singersshiftfrom using thefirsi formant for reinforcement to usinq higher formants, While in the lower voice they match a harmonic to the first formant of the vowel being sung, in the passaggio and above they lengthen the vocal tract by protrud- Figure 1. A professional soprano singing B, then using vocal fry (lower right cor- ing the lips and/or adjusting the posi- ner of the spectrogram) to highlight the location of vowel formants. Note the close proximity of the fundamental to the first formant. tion of the larynx downward slightly to match a higher harmonic to a low- ered second formant or to the singer's formant. This is what is commonly described as "covering." Brighter voiced singers like Luciano Pavarotti in his prime and Alfredo Kraus are good examples of male singers who use the second formant-dominant strategy in the high voice. Placido Domingo, on the other hand, tends to use the singer's formant-dominant tuning strategy (Figure 4). The importance of tuning the fun- damental or its harmonics slightly below a resonance formant peak. In order to keep the vocal tract inertive (which assists sustained vocal fold oscilla- Figure 2. The author singing the vowel /i/ on E. Note the strength in the second har- tion) and to keep the pitch change monic (H2) at 315 Hz (close to the first formant) and the twelfth harmonic (H 12) due to vibrato in phase with the rise at approximately 2000 Hz (in close proximity to the second formant). in amplitude that occurs as the for- mantis approached during each vibrato cycle (so that loudness rises How might singers and teachers approaching their maximum. And, and falls in sync with the vibrato), apply this information to singing as this note is below the passaggio, singers should not try to tune exactly repertoire? Here are a few examples: optimal vocal tract resonance tuning to a formant, but rather slightly below Baritone: "Bella siccome un angelo," involves tuning the second harmonic it. This often means singing a slightly Donizetti, Don Pasquale, sustained (H2, at 554 Hz) to slightly below the more open vowel, so that the formant final note of the cadenza on the word first formant (Fl) of a vowel. in question remains slightly higher "cor" on the pitch Db4 (277 Hz). Recommendations: than the fundamental or harmonic Suhglottal driving pressures are (a) Slightly increase abduction to that is close to it. highl y positive at this pitch level, avoid overdriving vocal fold vibra- 174 JOURNAL. OF SINGING Voice Research and Technology 0.8 0.4 L -0.4 .0J 0 400 9W 1O 1 Ft.4.l WAPoxy, F0 (K N2vS Figure 3: Vocal fold vibrational amplitude change as a function of fundamental fre- quency, due to subglottal pressure varia- tions in the vocal fold driving pressure. From Titze, Principles of Voice Prod ucriwi. Used with permission. tion amplitude with subglottal pressures; the singer might achieve this by focusing on air flow while singing. (b) Shade the vowel toward a more open form of /o/, so that the sec- ond harmonic at 554 Hz is close to but slightly below the first for- mant of the more open vowel (approx. 570-600 Hz). Exact shading will vary with each singer. Soprano: "Steal me, sweet thief," Menotti, The Old Maid and the Thief, climactic high note on "steal" Figure 4. The author singing the word para is on 1 4 (upper image) and using vocal on B's (932 Hz). fry on the same vowel shape (lower image). Fl 550 Hz, F2 'v 1540. Note that H3 Subglottal driving pressures are is in close proximity to F2. negligible or slightly positive at this pitch range. Optimal vocal tract res- onance in the female high voice and /o/ at approximately 890 Hz. This (b) Slightly elevate the larynx and involves tuning the fundamental fre- pitch is around the upper limit of use a wide, flat mouth shape, in quency (i.e., the sung pitch) to slightly where the sung pitch and the first for- order to raise the first formant of below the first formant, however, with mant can be tuned to each other. the vowel as high as possible. the fundamental so high at 932 Hz, Recommendations: • Tenor: "II mio tesoro," Mozart, Don the lu vowel in the word "steal" is (a) Slightly increase abduction as Giovanni, sustained notes on "vado" not appropriate, with its first formant needed to equalize the effect of on F4 (349 Hz). at approximately 370 Hz. In fact, no subglottal driving pressures; Subglottal driving pressures are speech production vowel has a first again, instructing the singer to slightly positive to negligible. Between formant at 932 Hz. The closest vow- use a high air flow might be one D4 and C5, subglottal driving pres- els are // at approximately 770 Hz way to achieve this. sures shift from maximally increasing NOVEMBER/DECEMBER 2004 175 John Nix vibrational amplitude to maximally BIBLIOGRAPHY where he worked with Thomas Houser and decreasing it. Depending on the tes- Austin, Stephen F., and Ingo R. Titze. Barbara Honn. Prior to his studies at Col- situra of the singer, the note can be "The Effect of Subglottal Resonance Upon orado, he received a Bachelor ofMusic Degree sung "open" or "covered." Vocal Fold Vibration.