I know it was a gift from God. My father was a preacher and my mother worked in churches all her life. My father had a very deep bass sounding voice and my mother had an in-between soprano voice. Not great singers, but they had great tones to their voices. I think that had a lot to do with it. Also, I really believe my voice was a gift from God. I believe if you take care of it, He will help you take care of it.
