The following factors determine this unique vocal quality:
The first is the actual construction or shape of our physical bodies, such as the spaces in our neck and head.
The second is our mind. How we think and can use our imaginations to create sounds.
The third is our emotions. How we can access and express our feelings in our sounds without disturbing function. For example, it is very hard to cry and sing simultaneously.
The fourth is our basic temperament. For example, whether we are a more excited person or laid back person, which would mean that we would naturally infuse our voice with more energy if excited or less energy if laid back.