Scott hit on something about the number system (Thanks Mike Dunbar).
http://www.jpfolks.com/forum/ubbthreads.php/ubb/showflat/Number/900087/page/1#Post900087

You can use any key that you feel comfortable with and it can always be transcribed to another's liking, hence the number system.

When I record for myself or record a demo, I feel most comfortable with key's A, C, D, E, but mostly B. I know that B is a pain to most, but I Capo the 4th fret on guitar and play G position. My vocal range is just right there.

Sorry that the URL above widened the thread, but I think that it's essential.