Sometimes a person has a soft palate that does not close completely, resulting in a voice with a nasal quality. The student will need to practice exercises to strengthen the closing of the velopharyngeal port. The velopharyngeal port is the entrance into the sinus cavities. This opening is closed when the velum (soft palate) lifts upward and backward, like a flap, touching the back wall of the throat. The best word to use is “hun_ga.” Say “hun_ga” and notice how the “hung” makes a nasal sound, but when you say the “ga,” there is movement in the back of your mouth. The movement that you feel is the velum lifting, thus closing off the soft palate. Practicing speaking or singing “hunga” on a scale and you will strengthen the closure of the nasal port. Also, this exercise can give you the awareness of the difference between an in-the-nose “hung” versus the non nasal “ga.”
Nasal singing is often confused for the forward, ringing vocal sound that is popular in pop music today. Most singers are trying to get the voice to vibrate forward in the mouth, with the velum port entrance to the sinuses closed. I often see young students sing in their sinuses, thinking that sinus singing is beautiful singing. They try to mimic pop singers without any real understanding of voice training. Alicia Keys and other pop singers sometimes wiggle their noses when they sing to get the air up to the roof of the mouth and vibrating into the bones of their face. An untrained singer might interpret nose wiggles as sinus singing. People who sing nasally are, also, often not connected to the core support of their body. Good singing is always core-connected; otherwise, the voice will have no depth or power to it. Some singers, especially country singers, use some nasality to get a “twang” in the voice. Indian singers sometimes use a little nasality as part of a vocal style. The use of too much nasality will reduce the singer’s vocal power, as the voice can get stuck in the nose. If you want a country western sound, use as little nasality as possible. If you use too much nasality, you will decrease your vocal power. A little bit of nasality goes a long way.

From the book “Vocal Yoga, the Joy of Breathing, Singing and Sounding.”