Hi Penelope,
I play guitar and sing in a (purely avocational) blues-based band that performs within a 100-mile radius of my home. This is likely not the kind of singing you're thinking of, but I have learned some things that echo Edna's advice. Singing, at first, is a matter of letting go. For me, this involved letting go of my "natural" voice. Speaking, I sound very much like white-guy-who-grew-up-in-a-cul-de-sac. If I sing with my natural voice, I sound very much the same. I had to learn to growl (we're talking about the blues), sing in a lower register, sing from the back of my mouth, and so forth. At first, I felt as if I was faking singing--singing in someone else's voice. After awhile I understood the voice was mine. There was no man behind the curtain. What one discovers is that the voice is an instrument, and you have to learn to play it, and play with it. This can entail lessons, or if you're just singing in a blues band, learning how to growl in the shower. You also have to learn control and, depending on your ambitions, technique, but first is letting go. By the way, when I was in a high school play long ago in a role that called for singing a song, the director cut the song out of my part after telling me I was tone deaf. I can sing (just the blues, but singing just the same) anybody can.