re scrump, some songs start on the key note and some on the 3rd. etc. We don't have problems generally if the keynote is the starting note. Also, we tend to hike the keys all over on a song til we find the right combination of voices, It can be problematic for me if i am leading and occasionally a song is pitched at the top or bottom end of my range (Let the Toast Pass C - top end, Spanish Ladies D - bottom end) thats when I sometimes get it wrong, the other is also shared with my two colleagues, every pint after the second raises the pitch half a note! As to tone deafness, it is about training, practice and hard work, put the work in and anyone, eventually, will be able to sing in tune, it requires hard work and committment if one isn't naturally gifted with a bit of a short cut.