I'd like to throw in there that vocal training is a large part of acting training as well. I took classes like this. In fact in one we spent the whole first semester doing a little stretching routine, laying on the floor and then "moaning" or vocalizing for about an hour. (In the follow up class we started working on words, phonetics, and speaking) The whole idea is that much like how we are trained and ingrained with behaviors from society, so too is our voice a history of expectations, trauma, ect. Simply the way we hold tension in our bodies we cut off certain parts from vibrating and this results in different sounds. By vocalizing openly we found our unimpeded resonant frequency so that we could unlearn our lifetime of habits (this also includes social habits that effect how we sound and connect with another-- e.g. not holding your breath in preparation to speak something you are planning to respond when someone else is talking, it opens you up to listen, or tension from being told to sit up straight as a kid) and physical trauma. Only then could we see all the possibilities so we could make choices about how we wanted our voice to be. Everyone sounded different after that class. Sometimes really intense emotions trauma and otherwise would be released as parts of ones body finally let go. I remember just bursting out laughing in the middle one day, and there were several days I cried. It was the most centering class I've ever taken. And after that I liked my voice, I liked feeling it in my body, like a friend giving a vibrating hug

If anyone is further interested theres a fantastic book we read called "The Right to Speak: Working with the Voice" By Patsy Rodenburg that talks in great detail about these ingrained vocal habits