From the recording The Prodigal's Lilt

The American Civil War has been also called "The Brother's War," and for quite literal reason. Wesley & William Culp are a prime example of how actual brothers were pitted against one another during the conflict.  Wesley was from Gettysburg and moved to Virginia to work. Fatefully, he joined the Confederate Army when the war broke out. Meanwhile, his brother William and his friend Jack Skelly were among those Gettysburg boys who enlisted with the 87th Pennsylvania.
In June of 1863, the brothers and Skelly were involved in the same battle at Second Winchester (Virginia) - fortunately, they didn't encounter one another on the field. After the battle, Wesley Culp's brigade headed north and, a few weeks later, found itself at Gettysburg.
"The Prodigal's Lilt" envisions Wesley Culp arriving home with some glimmer of hope that he would be able to tie up loose ends, try to mend the rift he caused by siding with the South, and - of course - deliver Jack Skelly's letter to Skelly's fiancee, Jennie Wade. As he'd read in his Bible many times, surely the fatted calf would be prepared for the wayward son, who would be welcomed back home with open arms and forgiveness.