[...] Zychlinsky has spoken to me and told me that you want to know my opinion as to whether you should consent to do further arrangements of The Rhinegold. Now, please, do not on any account be over-scrupulous about it. I cannot restrain the publisher from having all kinds of arrangements made; besides, once the full score and the perfect pianoforte arrangement have been published, it is all the same to me in what other form my works are presented to the common herd. If I have any interest in the matter, it is merely that these arrangements as well should be made with insight and knowledge. Indeed, I am of opinion that they might be very important and interesting coming from an experienced artist, but meaningless if a common ignorant arrangeur is chosen to do them. Accordingly, I am even inclined to ask you to agree to Schott's suggestions. The fact that the orchestra plays so important a part, and is for the most part as coherent as for a symphony, will make your task easy. [...]
Source: Letters of Richard Wagner, Vol. 2, selected and ed. Wilhelm Altmann, trans. M. M. Bozman (J. M. Dent & Sons, 1927), No. 461