Chris in Portland asks: "Would it be correct to say that the shape note hymns have kept to the more basic, gospel arrangements, even though multi-part?"

Shape note hymn arrangements are a mostly historical form, predating what you mostly likely would think of as "gospel" style. There are 20th and 21st century shape note songs, but they are written in the style which really comes out of the 18th century. I wouldn't say that the shape note style is particularly easy. It is less chordal than later hymn arrangements; the melodies of each part are more independent of one another than our modern ear is used to. It also includes "fugueing" tunes, which are not particularly simple and which I don't believe appear in more modern hymn-writing. (Please correct me if I'm wrong.) There are some "camp meeting" songs that were absorbed into the Sacred Harp and other shape note collections that are more "normal" and straightforward to sing.

The Wikipedia description here is pretty good: Origins of the music, although it doesn't really compare or contrast with other styles. Also see the Wikipedia entry Sacred Harp hymnwriters and composers.

I don't know about any connections of the genre with particular evangelists, but I'm someone who has come to shape note singing as a folk singer, not from a religious background. Maybe some others in this discussion will recognize some of the composers mentioned in the second Wikipedia article I've linked -- ?

~ Becky in Tucson