Many of my opera recordings are of obscure works, early 20th century. Anybody familiar with these: Ullmann - Der Kaiser Von Atlantis, Goldschmidt - Der gewaltige Hahnrei, Goldschmidt - Beatrice Cenci, Krenek - Jonny spielt auf, Krasa - Verlobung im Traum, Braunfels - Die Vogel, Zemlinsky - Der Zwerg, Schreker - Die Gezeichneten, and Korngold - several of his usual suspects. These are all hyper romantic works, German or Austrian, and all but a couple were issued as part of the late lamented Decca "Entartete Musik" series of composers and works banned by the Nazis.
All make for hugely interesting listening, and the Braunfels, in particular, is just gorgeous.