I didn't answer Stilly River Sage's question about "weak chest registers." Think of the voice as being produced by two kinds of muscles working in coordination (your vocal cords or folds.) One produces the chest register sound the other produces the head register sound. Your full voice is some combination of the sounds of these two muscles. You may have a "weak chest register" sound because 1) the chest register muscle is weak (perhaps for the reasons cited by Stilly River Sage, 2) the coordination between the two muscles is not good, with the head register muscles winning over the chest, 3) your vocal concept (what you think you should sound like) makes you use more of your head register muscle. The difficulty is you can't strengthen your vocal muscles by exercising them the way you would exercise your biceps or your abs. You can exercise them only by producing sound. Enter Cornelius Reid who discovered (or re-discovered) that by using different combinations of vowel sound (ooh or ah), pitch and intensity (or volume) you could activate and thereby exercise each of the two registers. Another set of exercises allows you to work on the coordination of the two registers. The ultimate aim of the exercises is to train the vocal muscles so that they are flexible and free to respond to what the singer intends to do with the song, his feelings, his attitudes, his motivations at the moment of singing without the singer having to demand a particular color, intensity, texture, etc. of the voice.