Something you might be interested in is Frank Wedekind's songs. He was the first "star" of German cabaret, but he abandoned it as soon as he could get his plays performed. There was a book of them (with music) but it wasn't in print when I tried to buy it some years ago. I don't actually like them that much because they are more obscene than bawdy, but of great historical interest, of course.

Since he's an important dramatist, I think the texts might be published somewhere; in a "Complete Works", if nowhere else.

Early cabaret in Germany was more morbid (in a way that was meant to be amusing) rather than political. I find a lot of it not particularly interesting.