Correspondence: Kenneth Wood Bozeman, Lawrence University, Conservatory of Music, 711 E. Boldt Way, Appleton, Wisconsin 54911, USA. E-mail: bozemank@lawrence.edu

(Received 8 January 2012 ; accepted 4 March 2012 )

LPV FORUM

Acoustic passaggio pedagogy for the male voice

KENNETH WOOD BOZEMAN

Lawrence University, Conservatory of Music, 711 E. Boldt Way, Appleton, Wisconsin 54911, USA

Abstract Awareness of interactions between the lower harmonics of the voice source and the fi rst formant of the vocal tract, and of the passive vowel modifi cations that accompany them, can assist in working out a smooth transition through the passaggio of the male voice. A stable vocal tract length establishes the general location of all formants, including the higher formants that form the singer ’ s formant cluster. Untrained males instinctively shorten the tube to preserve the strong F1/H2 acoustic coupling of voce aperta , resulting in ‘ yell ’ timbre. If tube length and shape are kept stable during pitch ascent, the yell can be avoided by allowing the second harmonic to rise above the fi rst formant, creating the balanced timbre of voce chiusa .

Key words: Close timbre , fi rst formant , harmonics , open timbre , passaggio , passive vowel modifi cation , singer ’ s formant cluster , voce aperta , voce chiusa , voice source

Introduction and overview

A relatively stable tube (vocal tract) length is nec-essary for consistent depth and balance of timbre in Western classical singing. Both tube length and cross-sectional area are responsible for formant locations. Effective tube length determines the general location of the entire formant set of a given voice. Formants one and two (F1 and F2) are most affected by changes of shape other than length (changes in cross-sectional area) and thereby effec-tively defi ne and differentiate vowels. Higher for-mants are less responsive to changes of shape other than length. Tube length is therefore a signifi cant factor in setting and maintaining the frequency of higher formants. These higher formants are drawn together to form the singer ’ s formant cluster (SFC) under certain conditions (low larynx, open throat, and narrow epilaryngeal tube) as described by Sundberg (1) and refi ned by Titze and Story (2). The relative stability of the SFC is a key element in consistency of timbre and of perceived vocal Fach . The pedagogic problem: Untrained males instinctively shorten the vocal tract upon ascend-ing, raising F1 in order to preserve the strong F1/H2 acoustic coupling of the ‘ yell ’ (3), a behavior that appears to be a universal, hardwired survival

trait. Yelling results in an increasingly pressed mode of phonation, a heavier (thyro-arytenoid (TA)-dominant) laryngeal registration adjustment, and inconsistency of timbre and perceived Fach . If vocal tract length and shape are kept stable, F1 locations will remain stable and the yell will be avoided by allowing H2 to pass through and above F1. This transition results in the timbral shift var-iously referred to as ‘ covering ’ or ‘ turning over ’ , and it facilitates a lighter laryngeal registration adjustment and a less pressed mode of phonation (4 – 6). Since the location of the fi rst formant varies by vowel, knowledge of the variety of F1 locations and their predictable F1/H2 crossings an octave lower becomes both an accurate means of assess-ing tube length stability and a reliable basis for developing effective strategies for training tube stability for successful negotiation of the passaggio .

Acoustic principles

Timbral transitions once thought to be the result of laryngeal muscular adjustments are caused instead by changing interactions between harmonics of the voice source and the fi rst two formants of the vocal tract. This is not to say that there is no source

Logopedics Phoniatrics Vocology, 2013; 38: 64–69

ISSN 1401-5439 print/ISSN 1651-2022 online © 2013 Informa UK, Ltd.DOI: 10.3109/14015439.2012.679967

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Vocal pedagogy 65

contribution to timbre, but the particular shifts of the male passaggio are primarily caused by harmonic/formant interactions. There is an audible effect when a harmonic passes through a formant, especially when a lower harmonic passes through formants one or two. The most notable of these effects occurs when H2 passes through F1, traditionally described as moving from open to close timbre, turning over, or covering. If tube length and shape are kept stable while harmonics rise, this H2/F1 crossing will occur at predictable locations within a given voice. While each voice is unique, formant locations are rather predictable per vowel within a given vocal Fach , usu-ally to within a half step. Indeed, formant frequency locations (assuming a stable tube length) are signifi -cant in determining vocal Fach .

Cardinal vowels ’ approximate fi rst formants and locations of turning (Figure 1)

Defi nitions

The principles at play in acoustic passaggio pedagogy are inherent in the following defi nitions:

Open vowel: a vowel with a high F1, such as / • /, / /, / /, with an inherently divergent resonator shape. (A divergent resonator shape is one in which the resonator is increasingly larger or more open at the lip end.) Close vowel: a vowel with a low F1, such as /i/ •or /u/, with an inherently convergent resonator shape. (A convergent resonator shape is one in which the resonator is increasingly narrower or closer at the lip end.) Open timbre ( • voce aperta ): sounds in which two or more harmonics are at or below the F1 of the vowel being sung. Close timbre ( • voce chiusa , covered, turned over): sounds in which H2 has slipped above F1 of the vowel being sung.

• Nota bene : Any vowel can be executed in open or close timbre, depending upon range, or pro-nounced more openly or more closely by raising or lowering its F1. • Chiaroscuro timbre: a balanced tone with both ring and depth, usually accomplished by some balance in power between F1 and a higher formant, either the singer ’ s formant cluster or F2, depending upon the situation or range. Turning over: the sound and sensation of H2 •slipping above F1; also called covering, closing, tipping, etc. Yell (call, shout): an open-timbred F1/H2 cou- •pling carried above the normal F1 location of the vowel being sung (Figure 2).

Intermezzo: yell characteristics

The yell is accomplished by raising F1 through tube shortening (larynx raising), pharynx narrowing, and mouth widening. It tends toward pressed phonation, is typically done on open vowels like / / or / /, and is chest register (TA)-dominant. This shortened, divergent res-onator shape is typical of most popular, folk, and world music, which can be described as more or less skillful yelling. It is clear and powerful but typically involves higher levels of breath pressure and glottal resistance.

Whoop (hoot): a strong F1/H1 coupling (3) •(Figure 3).

Intermezzo: whoop characteristics

The whoop or hoot is accomplished by tuning F1 to the H1 (F 0 ) being sung. It is falsetto (cricothyroid)-domi-nant, tends toward fl ow phonation, facilitates laryngo-pharyngeal space and a convergent resonator shape (both of which lower F1), and is primarily done on close vowels, especially /u/. Since women often sing pitches above the F1 locations of their vowels, they are often operating in whoop mode in Western classical singing.

Figure 1. This is a ‘ musician-friendly ’ charting of formants. In this chart, the approximate fi rst formant locations are notated on the treble clef with IPA symbols within boxes, while the pitches on the bass clef indicate the pitches above which each vowel would ‘ close ’ or ‘ turn over ’ . The historic location of the zona di passaggio as reported by Richard Miller (7), lies between the turning frequencies of the moderately close /e, o/ and the most open / / vowels.

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66 K. W. Bozeman

Vowel modifi cation: an adjustment of a vowel (a •retuning of F1 and F2 locations) accomplished by a reshaping of the vocal tract. Passive vowel modifi cation: a vowel shift that •occurs not from a shape change, but from the changing interactions between a stable tube shape (and formants) and rising pitch (rising source harmonics).

F1/harmonic interaction summary

Awareness of degrees of openness and closeness is crucial to understanding male passaggio . Vowel and timbral openness or closeness is related to the height of the fi rst formant frequency and/or to the relation-ship between lower source harmonics and the fi rst formant. It is therefore pedagogically necessary to understand the relationships between the fi rst formant and the harmonics of the voice source in some detail. To review (and elaborate somewhat):

When two or more harmonics are below F1, the 1. timbre is open and ‘ chesty ’ ; the more harmonics below F1, the more open the timbre.

When any source harmonic 2. descends through F1, there is a noticeable timbral opening. When any source harmonic 3. ascends through F1, there is a noticeable timbral closure; the fewer harmonics remaining the below F1, the greater the closure. When H2 approaches the peak of F1, it forms 4. a strong, open timbre acoustic coupling. If this F1/H2 coupling is taken higher through tube shortening, this becomes a shout or yell. Conversely, when H2 is allowed to pass through 5. and above F1, the primary timbral transition of the voice (i.e. turning over) occurs. An F1/H1 coupling (an octave higher than F1/6. H2) becomes whoop or hoot timbre and is ‘ heady ’ and full. As one ascends the octave between turning and 7. whooping, if the tube shape and F1 location are maintained, the timbre becomes increasingly close. If H1 is allowed to surpass F1, the voice thins 8. in timbre and weakens in intensity. Therefore when singing above the normal F1 locations, F1

Figure 2. F1/H2 coupling of open timbre.

Figure 3. F1/H1 coupling of whoop or hoot timbre.

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Vocal pedagogy 67

must be raised in tandem with H1 (8) to main-tain whoop coupling (F1/H1).

Objectives of passaggio training

The objectives of passaggio training include:

A stable laryngeal position and relatively conver- •gent resonator shape for consistency and depth of timbre. A dynamic laryngeal registration with smooth, •gradual changes for ease, evenness of scale, and dynamic fl exibility (all of which are facilitated by a stable laryngeal position). A familiarity with the sounds, sensations, and •locations of vowel turning. (Implication: Since turning has to do with fi rst formant locations rather than with laryngeal registration, it is erro-neous to think that a voice will turn over on the same pitch for all vowels.)

The ability to let vowels turn over at their nor- •mal resonant speech locations (an octave below their F1 locations). Vowel integrity with appropriate vowel modifi - •cation. Maintenance of • chiaroscuro timbre across range and transitions.

Pedagogic strategies conducive to effective vowel turning

Encourage a convergent resonator shape • , which will generate and maintain appropriately low F1 locations. This can be accomplished by several means. The initial means would be the use of a noiseless inhalation. A noiseless inhalation requires a relatively open throat and convergent resonator. However, fi nding this pre-phonatory posture is challenging for students since one ’ s kinesthesia for throat shape is quite misleading. Most people perceive / / to be the most open-throated posture and /i/ to be the least open-throated, when the opposite is in fact the case. To circumvent this false kinesthesia, a noiseless inhalation can be accomplished by a subtle pal-atal lift (incipient yawn) accompanied by cool-ing the teeth and front of the mouth upon inhalation, rather than cooling the throat. Wher-ever the vocal tract is the coolest it is the nar-rowest, since air speed will be the quickest and the resultant wind-chill effect the strongest there. Shaping the mouth and throat so that the cool-ing is in the front of the mouth causes the throat to be more open and the resonator more convergent. At the same time, shape the mouth and throat to lower the pitch of any inha-latory noise. A complementary strategy that encourages a convergent resonator is achieving a loose, fronted tongue, whose sides may even make contact with the upper molars. And a third strategy is to use minimal ‘ jawing ’ of diction, reducing excessive ‘ orality ’ . Vowels do not require exaggerated jaw drop or excessive articulatory changes in the lower and middle range; rather vowels can seem fairly close to each other. All of these strategies improve throat openness and a convergent resonator, lowering F1.

Figure 5. Leaping across the pitch of turning.

Figure 4. Thyro-hyoid space: just below the hyoid bone, laterally and posteriorly.

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68 K. W. Bozeman

Figure 6. Descending and ascending across the pitch of turning.

Monitor tube length stability. This can be accom- •plished by physically monitoring the thyro-hyoid space in students whose anatomy lends itself to easy identifi cation of laryngeal anatomy (Figure 4). The thyro-hyoid space should be loose and open and not rise or become smaller (as it does in swallowing) with pitch ascent. Though this space varies in size between individuals, it may also have been reduced in size by residual tension from unnecessary activation of swallowing muscles dur-ing speech production, a habit that, if entrenched, should be patiently but persistently countered and broken, preferably through therapy with a licensed speech language pathologist familiar with appro-priate therapies, such as massage and stretching of the thyro-hyoid space, monitoring of the looseness and openness of the thyro-hyoid space during speech production, and vocalizing with a low lar-ynx and an extended or ‘ rolled ’ tongue position. Secondly, tube length stability can be assessed by visually monitoring the location of the Adam ’ s apple. This method is more useful for males, due to their larger average laryngeal anatomy, and for those with less fl eshy, trimmer necks in which structures are more easily visible. Finally, tube length stability can be assessed by aurally monitor-ing the consistency of timbral depth/vocal Fach . This is less reliable, since it can be falsely mim-icked by various articulatory manipulations of tongue and lips, but careful listening and observa-tion can reduce this liability.

The following explorations can assist with the dis-covery and experience of vowel turning:

Speak an infl ective loop on the same vowel •across its predicted pitch of turning, staying

deliberately close in articulation. This is most easily accomplished on the close vowels /i/ and /u/, which turn over well below the passaggio , allowing the development of familiarity with the sounds and sensations of turning over indepen-dently of the laryngeal registration challenges associated with the passaggio . It can then be extended to include the moderately close vowels /e/ and /o/. On ascending leaps, encourage timbral depth, •vowel closeness, and an internalized direction and affect. These directives are all intended to preserve the vocal tract shape across the turn and to counteract the instinctive tendency to yell, with its shallowing (shortening), opening, and ‘ spreading ’ of the resonator. Glissando up from an open vowel on a low •pitch over a large interval to a close vowel on a high pitch to identify the kinesthetic and aural poles of openness and closeness (Figure 5). Repeat this on the same vowel across its pitch •of turning, anticipating, allowing, or if neces-sary, encouraging its passive modifi cation (Figure 5).

Strategies for refi ning vowel turning

Model the gradual timbral transition from close •to open timbre during scalar descent, followed immediately by ascent on the same pitches. The degree of openness/closeness of each ascending pitch should match that of the previous descent (Figure 6). Finally, ascend through the pitch of turning and •subsequently descend stepwise, allowing the

Figure 7. Ascending and descending across the pitch of turning.

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Vocal pedagogy 69

voice/vowel to close and then reopen across the appropriate pitches (Figure 7).

Conclusion

Knowledge of the effects of acoustic interactions between source harmonics and the fi rst formant of the vocal tract is crucial to male passaggio pedagogy. If tube length and relative closeness/convergence of resonator shape are maintained during pitch ascent, the location of the fi rst formant will remain stable, and the second harmonic will surpass the fi rst for-mant, appropriately precipitating the timbral shift of turning over. The variety and predictability of fi rst formant locations, and hence of F1/H2 crossings an octave lower, form a reliable basis both for diagnos-ing tube length stability and for crafting strategies for training the tube length stability necessary for effec-tive negotiation of the male passaggio .

Declaration of interest: The author reports no confl icts of interest.

References

Sundberg J. Articulatory interpretation of the singing formants. 1. J Acoust Soc Am. 1974;55:838 – 44. Titze I, Story B. Acoustic interactions of the voice source 2. with the lower vocal tract. J Acoust Soc Am. 1997;101:2234 – 43. Miller DG. Resonance in singing. Princeton, NJ: Inside View 3. Press; 2008. p. 50 – 4. Bozeman KW. A case for voice science in the voice studio. 4. J Sing. 2007;63:267 – 8. Bozeman KW. On the voice: registration strategies for training 5. the male passaggio. Choral J. 2008;48:63 – 4. Miller DG. Resonance in singing. Princeton, NJ: Inside View 6. Press; 2008. p. 61 – 2. Miller R. The structure of singing: system and art in vocal 7. technique. New York: Schirmer Books; 1986. p. 116 – 7. Sundberg J. The acoustics of the singing voice. Sci Am. 1977;8. 236:82 – 91.

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