So, my dearest Franz! Today I am sending you the completed first two acts of the “Valkyrie”; it gives me a profound sense of satisfaction to know that they will soon be in your hands, since I know that there is no one who is more sympathetic to my work than you are. I am worried that the second act contains so much material; there are two crises here of such import and such power that there is really enough material for two acts; but they are both so interdependent, and the one follows so immediately upon the other that it would be quite impossible to keep them apart. If it is presented as I require - and if all my intentions are fully understood - it is bound to produce a sense of shock beyond anything previously experienced. But a thing like this is written only for those people who can bear up under a certain strain (that is for no one!): the fact that the incompetent and the infirm will complain will certainly not be allowed to affect my decision. But whether it has all turned out satisfactorily - even according to my own intentions - only you can say; I can simply not do it any differently. In disconsolate and dispassionate hours what I was most afraid of was Wodan’s great scene, and especially the revelation of his fate to Brünnhilde, indeed, in London I was once on the point of discarding this scene entirely; in order to resolve the matter, I went back to my sketch once again and declaimed the scene to myself, bringing to it all the necessary expression; fortunately I discovered in this way that my spleen was unjustified, and that, on the contrary, a proper rendition produces a most musical and riveting effect. In certain passages I have given more precise indications as to how I intend them to be played, but there is a great deal still to be done, and it will one day be a major task to initiate some talented singer and actor into the very heart of my intentions by conveying my ideas to him in person. I am confident that you will see what is needed immediately. This is the most important scene for the development of the whole of the great four-part drama and, as such, will presumably soon receive the necessary interest and attention.
[...]
Source: Selected Letters of Richard Wagner, trans. and ed. Stewart Spencer and Barry Millington (W. W. Norton & Company, 1988), No. 190