I have to warm up an amateur SATB choir, and I'd like to do a bit of playing around with solfege. Over the course of the exercises, I'd like have singers go from a low to a high "do," or a whole octave. So, my question is this: what key is best to accommodate the ranges of all singers? (For example, if I were to start on a G, some tenors may not be able to hit the G2 if they wanted to start low and some might not be able to hit a G4 if they wanted to start high.)
What key, if I tell people to sing in their most comfortable octave, is most considerate of all singers and voice types?