wow.  thanks so very much for explaining this, and doing so in a very straight forward and easy to follow way.

ah!  the Scale part of that is the one that eluded me.  for some reason i looked in the "Node Reference" under "Range" (i was just grasping at straws) but didn't try "Scale."  whoops, and looking at it now, i don't see it listed.  i realize it's not a node, but i was thinking that since Wood and Marble weren't precisely nodes, that was really just the API reference.

so, i guess my question is this: what if you don't know the values of "lo" and "hi".  that is, if you have some node and it's producing a range of numbers/colors, and you don't know the precise value it starts and ends on.  and what if "hi" and "lo" are colors rather than numbers?  that is, would it matter in terms of finding those values if you were working with grayscale output or not?  i'm thinking it woiuldn't, but it's always better to ask.