I bought The Rebel Yell Lives CD last year just before the Chickamauga 150th, and I mentioned it to one of the other spectators while we watched the event from the top of one of the ridges that enclosed the valley below where the fightin' was going on. So, of course, I then was compelled by honor to give a demonstration, now that I'd brought it up. I mustered a little air and gave it my Rebel best.
Actually doing it, I found that the yip/bark component was very reminiscent of the kinds of group grunts and chants that are favored by the military to this day - and in feeling it is a far cry from the old Yee Haa's we all know and love. So I can say that it would certainly work for its purpose.
The CD is chock full of fun, too - they play with overdubbing the sound from the original recording to create different impressions of regiment, brigade,etc. They also create a stereo recreation of an indecent at the Wilderness if memory serves where the Union lines hurrah's were answered with the Rebel Yell moving up and down the Rebel lines.
They finish the CD off with a recording of Arturo Toscanini and the NBC Orchestra in Richmond Virginia in 1950 when, for an encore, they burst out with a very rousing rendition of Dixie - the crowd goes wild.