@farmerman,
Origin in early 1700 English Country Parishs. Migrated and expanded within NEW ENGLAND in the mid and late 1700's. Moved South, mostly piedmont and low country Baptists Parishes in the 1800's . Apparently today theres only a minor presence of "Sacred Harp" music in the AppalACHIANS.
When I worked West Va for MAdison coal companies, We would go and listen to Sacred Harp concerts near Mingo after the Baptists services were over. It was an interesting kinda weird sound, almost like throat singing and some unusual harmony.