This article is 2nd in a series on the Male Voice Passaggio.
In the first article in this series, I explained the acoustic basis of the male voice passaggio experience. In short, the passaggio is a place in the range where the resonance characteristics of the voice are 'between' those of the so-called 'chest voice', and 'head voice'. Of particular interest is the relationship of the first hamonic of the sung tone with the lower vowel resonance.
In this article, we will examine some of the resonance strategies available to the male singer in this range, and how those strategies help consistency of vocal tone, power and ease-of-singing.
'Chest voice' power... to a point
As mentioned in the prior article, a great deal of the power of the voice, and the sensation that the voice is 'in the chest' comes from the strength of the lower harmonics. This situation continues during the upward scale until the the 2nd harmonic passes F1, the location of which varies by voice type and vowel. Singing upward from there, the 2nd harmonic rapidly loses power halfstep-by-halfstep, and since the fundamental is an octave below it, there is now no strong resonance in either of them from the lower vowel resonance. The 'bottom' (powerful low resonance) has fallen out of the tone quality, and the sensations of that resonance in the chest and other tissues, becomes rapidly much less. The sensation for many is that the voice has 'left the chest'. Also, since the middle harmonics are farther apart in frequency now, F2 has not yet been of an advantage to make up for the missing power of the lower harmonics. In another way of putting it, the singer is no longer in the chest voice, but not yet in the 'head' voice.
This change in resonance character and power does two things to the singer, one at the laryrngeal level, and the other in tone quality: 1) it removes the cushioning provided the vocal bands by the inertive vocal tract, and 2) it causes a tone quality change which favors the brightness (singers formant component) of the tone. Item 1 makes the voice less stable (sensitive to disruption, for example, cracking, blips, etc), and item 2 makes it brighter by comparision to the notes immediately below it, without having any satisfying vowel resonance.
Arriving in head voice
Continuing the scale, the male singer reaches a point where F2 finally aligns with the 4th or 3rd harmonic (depending on vowel) and F2 greatly strengthens this harmonic, to the point that it is the most prominent in the entire voice. Very often, this circumstance is accompanied by pronounced sensations in the bones of the front of the front of the face, and very often elsewhere. For the singer, the voice is now fully 'in the head'.
In effect, the passaggio is the section of the voice between these two distinct areas of resonance characteristics, above the area where F1 helps the 2nd harmonic, and below the area where F2 helps the 4th and 3rd. When the word 'passaggio' is used to mean an active technique, it means whatever is done to keep the vocal quality consistent in this area, and also keeping it from becoming unstable. In other words, to connect the secure, powerful lower and upper voices in a manner that makes the voice as consistent as is possible.
Passaggio resonance strategies
A) Principal among these is the use of epilaryngeal resonance, in either the form of twang orsingers formant, which we might describe as twang with classical vowels. This has several desirable effects.
1) The use of this resonance boosts vocal power by ~20dB (that is, greater than 8 times as loud to a listener,) particularly by increasing the volume of harmonics in the 2500 to 3500 Hz region, the most sensitive range of human hearing. With this resonance, the singer gets much more sound, and much more audible sound, from the same amount of effort, and can thereby be heard effectively without having to push vocally. More sound, more apparent volume, less work. Sounds like a winner to me.
2) Epilaryngeal resonance, which occurs in the small space immediately above the larynx, before it continues on to the upper parts of the pharyx, provides a cushioning acoustic feed-back to the vocal bands, so they do not take so much stress as they go through their motions. For the techies out there, it can be thought of an impedance-matching layer between the vocal bands and the pharynx.
In common parlance, 'riding the vocal ring' across the weak area. For the classical singer, its often the region where vowel darkening (via modification, discussed later) is done to counteract the brightness of the rising-voice tone quality, a technique which to some extent increases the intertive character of the vocal tract, providing some helpful cushioning.
An epilaryngeal resonance strategy is not only helpful in the passaggio, it has these effects in the lower and upper voices as well. However, in the passaggio, it provides much-needed tone quality consistency while the vowel resonances are 'between gears' so to speak.
Vowel Modification can be used to advantage. There are two approaches here to be mentioned.
1) Because the passaggio starts and ends at different notes for different vowels, the singer can benefit from shading a vowel which has become unresonant toward a related vowel that is not.
For example, the first vowel resonance for /i/ (ee) is lower than it is for /I/ (ih). The passaggio for /i/ starts lower than it does for /I/ in a given voice. If done gradually, the singer can shade the /i/ progressively toward /I/, which the listener will not notice because it sounds so well.
Acoustically, the effect of this maneuver is to raise the first vowel resonance, and lower the 2nd vowel resonance, bringing them closer together. This technique can be used by singers who use low, medium or high-larynx approaches. The vocal tract retains most of its inertive quality because vowel resonance is being maintained with these alternate vowels.
2) Vowels can also be modified by changing them to more 'closed' or 'darker' forms on the ascending scale, so that both the vowel resonances are lowered. In some circles,this technique is called 'covering', and if done well, is not noticable to the listener. If it is noticed, it was overdone :-)
In this approach, vowels such as /a/ (ah) are modified to aw, and /o/ (oh) toward /u/ (oo) through the passaggio. Other vowels have their own series of similar modifications. The technique is generally usable with classical vowels, and with lower-larynx technique, without objection by a listener. If done by a mid-or high-larynx singer, the tone quality variation would likely be more obvious if not done very subtly.
The effect of this type of vowel modification is twofold:
---to create a lower position for the first vowel resonance, and to bring the second vowel resonance downward so that it will align with harmonics 4 or 3 sooner than it would otherwise, and
---to increase the inertia the air in the vocal tract, making it more cushioning for the vocal bands
Either, or both of these vowel modification techniques can be used by the singer to create the tone quality effects that suits their artistic expression.
Passaggio Width and location
As a practical matter, the passaggio region for any vowel is about a perfect fourth wide. The starting point will vary by voice type and vowel. /i/ (ee) and /u/ have the lowest passaggio entry points. /e/ (ay), /I/ (ih), /o/ (oh) and /E/ (eh) have the next lowest, and /a/ (ah) has the highest. Other vowels are spaced between these.
Passaggio locations are a general indicator of voice type. Bass has the lowest passaggio point, baritone somewhat higher, and tenor highest.
Conclusion, or the Benefits of Passaggio technique
Why bother with all of this? It makes singing more consistent, powerful, enjoyable to do and pleasant to hear. It reduces vocal strain, and increases tone quality stability in a region of notes that can be fraught with problems for the male voice. There are several approaches from which to choose, and the singer can combine them in whatever way makes sense for their vocal endeavors.