It should be the Battle Hymn of the Republic, just with some of the original lyrics:

John Brown’s body lies a moldering in the grave

John Brown’s body lies a moldering in the grave

John Brown’s body lies a moldering in the grave

But his truth keeps marching on

or

We’ll hang Jeff Davis from a crab apple tree

We’ll hang Jeff Davis from a crab apple tree

We’ll hang Jeff Davis from a crab apple tree

John Brown’s truth keeps marching on.