The King's Singers - an unlikely folk group - recorded two discs of German folksongs in 1978, including the beautiful, simple song Annchen von Tharau. According to their website,these are now permanently out of the catalogue. Pity. As a resource, there are the worlds of a large number of German folktunes, and those of other countries, with synthetic renditions of tunes on the website http://ingeb.org. You probably already know that site. I will be in Berlin early November. If I see anything suitable, I'll let you know. Unfortunately, I won't have much time.