Was listening to Stupel's recording of Langgaard's 3rd symphony and wondering if he may have been inspired by Gade's fifth to add a piano? Apparently, the piece began as a concerto/fantasia, and morphed into what we have today. I'm not very familiar with Langgaard's biography, and don't know to what degree he may have been influenced by Gade. Personally, I tend to hear more Strauss than Gade in early Langgaard...