I have several different versions of the Musette from Bach's Anna Magdalena Notebook, and there seems to be a difference of opinion about the left-hand notes in bar 18.
Some of my copies indicate an "e" as in the image below, but some have a "d" instead. If only one version differed, then I would go with the others and just assume a typo, but I have about equal numbers favoring each version, so I am unsure.
Both versions sound reasonable to me, so I would appreciate an expert opinion as to which note I ought to be playing here.