Singing is something that's special to each individual...If one feels that a particular part in a song should be sung softly and gradually build the tension and emotions up with a gradual crescendo, than do so, no matter how soft the start may be. There's no 'set volume' for singing, It's however you wish to interpret it. Unless of course, if someone were to hold back, not because they thought that the song called for it, but because they were afraid of what others might think, that's kinda sad, for both the audience and the singer. If you love to sing, and you WANT to sing, DO IT DAMMIT! None of this half-assed crap, 'cause that's not what people want to hear, and that's not really what you want to sing. If it comes from the heart, I'm sure it'll be loud enough for anyone that wants to hear. The more fun you're having, the more your audience will be touched by your singing, even if you feel that it's not necessarily any better than when you sing roboticly.
Always add your own flare, even if you're somewhat trying to sound like that original artist, put some of you're own feelings in there. Don't worry too much about control, if the emotions are welling up inside, just let them come out, You'll find that doing that will somehow (I think by magic) momentarily increase you're range, volume, and every other positive attributes. So don't like, try to bridal them or anything you might end up sounding stuffy... perhaps constipated...^^ Just lay it out.
Anyway, Have fun, 'Feel the music' No matter how corny that might sound...It's true, and fine tune your style according to your own interpretation of the song.
