IIRC Sammy was pretty good with a drum set (and in any case, before his hip went out, could give any drummer a run for his money with a pair of tap shoes). SDJ, in fact, is my nominee for the best all-around entertainer of the last century. Dance, singing, acting, comedy/impressions. Vaudeville, cabaret, broadway, vegas, film. I can't think of anyone else who covered that much as well as he did.
Their instruments were, of course, their incredible voices they were blessed with. And in Sammy's case, he also had the drums as well as the damnedest pair of tap feet ever known to man.
And that was the key: Just like Alice and Ozzy, they gave you a show of both talent and showmanship, and a hell of a one at that.