I'm looking for some interesting, preferably melancholic or else not "happy". Most German folk music I hear is the same Southern oomp-pah sound, and I know there's gotta be more out there. I'd also prefer it not be a classical arrangement (for piano and voice), but I'm not totally against it.

An interesting question, and although I can't help you specifically, I'm joining this thread because I'm interested to see what suggestions come up.

I've been exploring traditional European folk music for many years, and Germany does seem to be a big Oompah-shaped hole in the middle. I have plenty of stuff from the outer edges of Europe: Sweden (Groupa, early Hedningarna, Väsen), Finland (Värttinä), Latvia (Ilgi), Spain (La Musgaña).

Check out those acts if European folk music in general interests you, but I'm afraid I have nothing from Germany. Good luck!

The only I know of is Waldteufel aka Markus Wolff; but it's modern folk, dark and ritualist:

https://youtu.be/SIp3AHXLwC4?list=PLbB1 ... _XaFQQViST
https://www.youtube.com/watch?v=7X80Rp8ZQGI

It is indeed a difficult question, and I'm a bit heartbroken that Germany, for the most part, doesn't have awesome folk music like all the other European countries.

That said, your best bet is the folk music revival of the 70s, with bands like Ougenweide, Witthüser & Westrupp, Liederjan and Zupfgeigenhansel. Maybe also Hölderlin could fit the bill.

Also, your question reminded me of this collection that I've been meaning to check out for ages, that's supposed to contain non-sucky music from the Alps region. It looks like most of it isn't actually German, but rather Swiss or Austrian, if that's also okay. Most or all of the individual tracks seem to be on youtube, but there's no playlist.

Some of this stuff will probably still be too "happy" sounding for what you're after. There is of course also lots of medieval stuff, but I suppose that's not what you're looking for either.

Just remembered something else that might fit the bill. Empyrium's Weiland is (semi-) acoustic, melancholic and has lyrics in German.

What about Heilung? They're definitely not oompah
https://www.youtube.com/watch?v=h1BsKIP4uYM

Odroerir - Das Erbe unserer Ahnen
https://odroerir.bandcamp.com/album/das ... erer-ahnen

Wöljager - Van't Liewen Un Stiäwen
https://woeljager.bandcamp.com/album/va ... un-sti-wen

Nebelung (all)
https://nebelung.bandcamp.com/

Sturmpercht - Geister im Waldgebirg
https://sturmpercht.bandcamp.com/album/ ... waldgebirg

I know the latter is an Austrian band but you will surely enjoy

Seconding the Nebelung rec. Their Vigil is one of the best albums there is.