An afterthought. As noted in my remarks on Creating "Der Rosenkavalier, Harry Graf Kessler was said to have known "everyone." Two he seems not to have known, however, despite extensive French connections, were Louis Artus (1870-1960), librettist of the forgotten Ingénu libertin (1907), and Claude Terrasse (1867-1923), the composer.
Is it possible, I wonder, that the debt of Der Rosenkavalier to their Ingénu libertin never came to their attention? Surely they must have known that the opera existed. From the Dresden premiere in 1911, the work went on to conquer the world. It reached the Teatro alla Scala in Italian within two months. The United Kingdom premiere at the Royal Opera House followed in early 1913. The Gallic world was slower out of the box. Monaco introduced the French translation in 1926, a year ahead of Paris. Terrasse was gone by then, but Artus was still going strong. Could Le Chevalier à la rose really have failed to ring a bell? If not Artus, wouldn't someone have noticed?