I've heard of the tap test, but I don't really know what people are talking about. Now if I hold my Rhoads build at the crotch with my ear to the headstock and knock on it from the bridge area up the neck it kind of sounds like a bongo or some kind of mid to high pitched African drum, except it rings out longer. Neither of my Jacksons do this, they have more of a sharp thud that tails off almost immediately. They have great sustain, when played, so I guess I might be doing it wrong?