Vince, if you google it you can see a few videos of guys using them during hunts. I think his hope behind this call is to stop an antelope if it is trotting away, kindve like a single click for a turkey to stick his head up kindve a deal.
He knows it may not be the most useful call, but nevertheless he is still wants it in his vest when he goes on this trip.
Ive only hunted antelope one time, and I never got closer than 225 yards from one (alive). So as far as their vocals, I have no idea