Hi toadfrog,

be sure that your char code is Western (ISO-8859-1) before reading

NOT "Abends" BUT "Gestern"
NOT "in den" BUT "in das"
NOT "Mägtelein" BUT "Mägdelein"

Hearing Martha Schlamme sing 203 Bei Mondenschein it was no wonder that I didn't find the song with your beginning.

It is in ingeb.org
in a slightly different version, seeming to be incomplete (Mägdlein, was machst du hier ... missing)
3. NOT "ich bin", BUT "ich bind'"

In another link I found it listed in a songbook which we don't have in the university library - but! I own it myself and shall look it up this evening. If it is really in there you'll get the words soon.