I have to get the kids to school, but one quick note. The higher voice has a different tone than the lower voice. There are songs I learn off of tape etc. which are easily in my range but are at the higher end of an alto's range. I pick up that quality of strain, or whatever it is, when I'm singing it and find it harder to hit notes which should be easy. I have to consciously stop myself and reassess before I can sing easily.