I was struggling to come up with an example of immoral songs from the Weimar period.

Why struggling? It was a huge mistake to say Lili Marlene was a prostitute! Not “I may have been wrong …” but you definitely were wrong. Here are the English lyrics:

Underneath the lantern
By the barrack gate,
Darling I remember
The way you used to wait.
T’was there that you whispered tenderly
That you loved me;
You’d always be
My Lili of the lamplight,
My own Lili Marlene.

And in German:

Vor der Kaserne,
Vor dem großen Tor,
Stand eine Laterne,
Und steht sie noch davor,
So woll’n wir uns da wieder seh’n,
Bei der Laterne wollen wir steh’n,
Wie einst, Lili Marleen.

It’s a love song about nice girlfriend of a soldier, not a prostitute selling her wares under a street lamp. And naturally, if they met and kissed and spoke to each other under the streetlamp, they weren’t even having sex. That was not common among young people in Germany, where show of affection was tantamount to a marriage proposal!

For my part, I was trying to express the wholesome activity of group singing that young and adult people used to engage in (and not smut songs either; maybe just a little suggestive sometimes) … as so distinct from our entertainments of today.

I was struggling to come up with an example of immoral songs from the Weimar period. I think the film Cabaret probably gives just a mild hint of that.

Here are what Richard Wallaschek and Willie Ruff (a Negro) had to say about the White origin of “Negro” music: How long have scholars known that Negro spirituals were a hoax?