The original melody of "Under der linden" may be preserved; the melody of an anonymous old French folk song entitled "En mai au douz tens novels" fits the meter of the poem, indicating that "Under der linden" may actually be a contrafactum of "En mai au douz tens novels". Though this contrafactum is possible, it still remains uncertain.
"Under der linden" is a famous poem written by the medieval German lyric poet Walther von der Vogelweide. It is written in Middle High German. The song may have originally been sung to the surviving melody of an old French song, which matches the meter of the poem.
Looking at the text of the song it is immediately clear that this is NOT a text fit for a class A family website!
All kind of things are going on beneath the green tree....
As evidence I present a sketch which only begins to hint at all the poor tree had to witness!
For those whose curiosity is roused, here is the text of the poem: