The Rebel Yell has been the source of a considerable amount of debate. We're not even sure what it sounded like, or if it had a generic sound or was totally improvised in nature and varied from battle to battle and army to army. One Confederate veteran, when asked to reproduce the sound after the war, said "It was impossible unless made at a dead run in full charge against the enemy." To me, that would seem to indicate a spontaneous outburst born of nervous tension, fear, rage, etc.