Graham,

The rule of thumb, at least according to my community college vocal instructor, is to pick the highest note that you are comfortable with in a particular song, then work from that level down.

There are no rules etched in stone as to which chord you select to sing a particular song. You just work in the confort zone. Works for me!

Cheers,

Gary
_________________________
PSR-S950, TC Helicon Harmony-M, Digitech VR, Samson Q7, Sennheiser E855, Custom Console, and lots of other silly stuff!

K+E=W (Knowledge Plus Experience = Wisdom.)