Silence or rests are very powerful communicators in singing. I discovered that when I started to do a capella stuff.

Boy, it was scary to not have that guitar available to fill the gaps when you forgot a line. But the power of unaccompanied singing is, I think, unmatched. When I listen to field recordings of, particularly, the singing of prison work gangs, they tend to send chills up my spine. The great gospel quartets also affect me that way.

Come to think of it so do Gregorian Chants and Almeida Riddle, Dee Hicks, and many others.