It was spalted maple, the top of the guitar was. That was what the tag said. The floor manager hung it up with the other guitars, and those of us who were gathered around admired its spaltedness. I had no idea what spalted meant, but the wood was startlingly unlike anything else in the shop. It looked as though a slightly mad artist had picked random lines out of the wheat-yellow grain and had carefully highlighted them with a fine-point black fountain pen. It was very spalted indeed. (I have to use that word ad nauseam now because I had never used it before in my life until yesterday and I now feel obliged to make up for lost time.)
As you can read here, spalting is actually the earlier (and rather more attractive) stage of wood decay. Those wonderful black lines are actually the pallisades that "form when incompatible colonies of fungi come into contact with each other and lay down barriers to separate their territories." That makes fungi sound rather vicious and not quite so much. . .fun, eh?
The page I just quoted, that of the Ohio Department of Natural Resources, is well worth a perusal, as it describes the spalting process in fairly concise detail, and even gives spalt-it-yourself guidelines, for those so inclined.
But all this wonderful description is a bit cart-before-the-horse--I should have started at this page where you can see several examples of the phenomenon. While I'm at it, here's the guitar I started jabbering about in the first place, the Ovation CC44-SM, though the picture here doesn't show the spalting to its best effect.