The Passagio: Myth vs. Mechanics
What is it?
The passagio is a necessary change in the dominant muscles responsible for making a pitch.
What is happening?
Put simply, the pitch is determined by the length and tension of the vocal folds. Lower pitches rely predominantly on the speaking muscles or thyroarytenoid muscles(TA's), the deepest layer of the vocal folds, which bulk or mass the folds. As you ascend in pitch there has to be a transfer of dominance from the TA's to the crying muscles or cricothyroid muscles (CT's), which tilt the top half of the larynx (thyroid cartilage) forward. This tilt stretches and thins the folds, which aids in creating higher pitches. Singers often experience a change in the location of the sensation of vibration (chest, throat, mask, head, etc.) when moving around the passagio. This change in sensation is determined by the sound the singer is making and in what part of the range and will vary between sound qualities and singers. It is important to note that this change in sensation of vibration is a by-product of the muscle set-ups the singer is using, not the cause. It is difficult to teach by where a singer feels the vibration and get sustainable results. Singers are more likely to find consistency in their voices when they are given tools that help them isolate the muscles that are responsible for different sounds. This way they can always tune-in to how they are making the sounds happen as opposed to judging the sound by where they feel the resulting vibration.
Why make the change?
If a singer wants a more consistent aesthetic sound quality throughout the range this change in muscle use has to be made gradually and subtly by adding the CT's in before the singer reaches the passagio. The singer must then also gradually reduce the amount of TA effort as he/she ascends over the passagio. The singer may also choose to add twang or an aryepiglottic sphincter contraction along with contractions in other muscles in the pharynx to give the voice an edgy or ringing quality that will boost the formants between 2.5-4kHz where the ear is most sensitive. This twang will make up for any perceived diminishing of power that accompanies the thinning of the vocal folds as the singer moves up in the range.
Why not make the change?
This decision to blend the qualities above and below the passagio is a purely aesthetic one. Many a singer has benefitted from the use of falsetto or belting (if applied correctly and safely) for artistic purposes and ignored any sense of aesthetic balance throughout the range. A blended or connected sound is more important in certain styles of music than others. Great singing is not purely the ability to sing high. It is a great worry to me that so many voice teachers are obsessed with four-octave ranges. This vocal size-queen approach to the range is often limiting to singers artistry and is often misrepresented as the only way to vocal health. It is also a very limited view of the myriad elements that make great singing exceptional. All sound qualities from operatic tone to belting can be employed safely and sustainably throughout one's range if one has proper muscle control. People who claim that bridging techniques are the lynchpin of sustainable healthy voice use often do so because it helps them sell their training products. This vocal scaremongering is without evidence and should be questioned if not discredited full-stop.
What should be considered?
Singing styles that require a modal or full-voice sound in higher parts of the range that maintain a conversational tone quality (pop, some theatre, RnB, etc.) will certainly demand that singers can move seamlessly through the passagio. Styles that rely on heightened states of emotion signified by vocal breaks, yelling, belting, distortion and breathiness (modern theatre, folk, jazz, rock/metal, etc.) will require singers to have access to a variety of sounds both above and below the passagio. These sounds will not always blend and may not be to everyone's taste. That does not mean one cannot make them safely.