She talked of Garryowen where General Custer (what she always called him though his rank had been lowered after the end of the Civil War as it was with all the officers) often used it as he and his men would ride in or out. It was the official song of the Seventh Cavalry.
And then there is this one which I have always liked. Romantic and again would seem something that would inspire as the men went on a long march or ride.
When you write, want the feel of a period in history or an emotional truth, music often is the key.