When I was young, I was able to emit a high pitched scream that may have sounded like a Rebel Yell. As I aged, I lost that ability. I imagine the same is true for these veterans. I understand that the Daughters of Confederate Veterans have a Gramophone cylinder of the Rebel Yell recorder earlier. It is in Richmond and they won't let it be played.
Of course when I was young I thought the Rebel Yell was "Yeee Hiiii!".