The Ian and Sylvia version (the one I learned so many years ago) is a cappella. Being a two-voice song, one voice does a basic melody while the other harmonizes. On at least one verse I&S switched voice roles which changed the overall sound of the song. I've always found it to be one of those songs that grabs your interest from both the sound as well as the story.
There is at least one Confederate soldier version with similar lyrics. The publication I saw it in credited the lyrics to a lady back in the post-war nineteenth century.
I've taken the best parts of both lyric sets, done a little re-writing to place the events in Mississippi and Tennessee and do it single-voice a capella in some of my Confederate music programs. I use my lyric version to illustrate how the initial fervor for war had become somewhat dulled by 1862 when the battles became really bloody affairs with many casualties, e.g. "We fought for nine hours fully until the strife was o'er / The like of dead and wounded I'd never seen before." Songs such as this will grab the attention of the audience, especially if they're kids in the 5th - 9th grade, since it gives them a somewhat memorable and dramatic way to learn history that they otherwise don't really care about.