Malcolm, don't feel bad. You're not alone. Boolean can be crazy! 2 binary state variables (1st= 0 or 1 and 2nd = 0 or 1) into a Bollean black box can give 16 different outputs. 6 of these are useless for doing anything worthwile, leaving 10 to play with. AND (inverse = NAND), OR (inverse = NOR), (exclusive or =) XOR (inverse = NXOR), then there are the 2 I just call B and C selectors (and their inverses). Some of these possible outcomes have reasonably standard names for the Boolean black box that give that result (AND, OR) but some have more than one (exclusive OR and its inverse), and some don't have any (those B and C selectors). The way Boolean algebra is treated in most textbooks is just crazy.
After my complaint that they had missed the 17th century copy of "Death and the Lady", Wood 417(129) (ZN843) they went and found it and put it on.
However, I also complained that "The Young-mans Lamentation" Douce 2(261b) [search title on 'young-man'], the origin of much of "On Top of Old Smokey", is mostly unreadable has brought no results. It's still mostly unreadable. (ZN3614 in my broadside ballad index)
There are also a lot of other unreadable sheets.