Thanks for the suggestions! Maybe adding the lambic would work, but I don't think I've quite explained this how I meant to. I guess I'm not looking for a "tangy" flavor per se but more of a malty bite or sharpness? For instance, the owner of the LHBS suggested I add a little rye, and the recipe...
That subject line is a bit deceptive--I don't actually want the flavor of copper, but I am asking for advice on what grain (or whatever) could add the equivalent of the kind of zing or tang you get when you put a penny in your mouth (as one does). It's kind of hard to explain... I don't want it...