I was tickled by this report of the music committee for a past FGC Gathering. It is meant as a suggestion to future music committees and follows descriptions of other singing opportunities at the Gathering. It is as accurate and succinct description of Sacred Harp singers as I've ever read. (The line breaks were in the original; it reads to me like a poem.)
Shape Note/Sacred Harp.
They need to stand in a square and have good live sound.
They like a space with lots of resonance, not drapes and carpet,
where they can be loud.
If they don't like where you put them, they'll find their own space
and leave you a note.
They are very self sufficient.
They do not need a piano.