As a choir warm up, we sing Amen, it holds there voices, out and like I normally say,"Alright time to start and get them cob-webs out". It's easy and easy for a musician to pick up. It's in the key of C.
You can do it 2 ways: 1) as a 2 to 1 beat song {A.....MEN, A.....MEN......A...A....A....A.....MEN} It transpose up, from 0 to 4 at least.
CHORDS: your musican can always add what he needs this is just basic, and it can always be changed.
LH/RH key: C
I'll post a video, of it when I get my piano back from the shop ha