Back in the early 1900's when Cecil Sharp collected ballads in the Appalachian region he noted that none of the ballads were sung with any instruments. There were a few dulcimers, banjos and fiddles around but they were not usually used in the singing.

The guitar arrived in Appalachia around the time Sharp visited in 1916.

It seems hard to believe now but the traditional style of ballad singing used no instruments.

Doc Watson occasionally sings a song or two without playing at his concerts, singing in the "old way."

Yes, the shape note singing is similar except the texts are usually prepared.

-Richie