The amplification of these particular harmonics is believed to be a result of a narrowing of the Aryepiglottic fold just above the larynx. Voices with naturally acquired squillo, i.e.
The phenomenon of amplifying these particular harmonics is thought to be caused by a narrowing of the Aryepiglottic fold just above the vocal apparatus, resulting in voices that exhibit a natural brightness or luster, which can be described as having a certain quality or character.