I cannot deny that my opera [Rienzi] presents great scenic and musical difficulties in performance. I consider one of the greatest of them the effective division of the male chorus into the two groups, populace and nobles. The choruses which are to be sung off the stage must necessarily, I suppose, be sung by the choir of the Kreuzschule. Anyhow, in planning both scenes I only reckoned on this material, since the first chorus is wanted to make a strong effect at the same time, and this would be impossible if the theatre choir were to be divided. The big tragic pantomime at the finale of the second act offers another difficulty. In my view the parts of the principal characters in it, Lucretia, Brutus, Tarquin and Collatinus, cannot possibly be taken except by actors accustomed to play similar characters in the spoken drama.
Among all the many things which I think would repay discussion I will only mention the chorus of the heralds of peace at the beginning of the second act. This chorus is not an easy one to sing unaccompanied, so only those members of the female chorus who are most musical and have the best natural voices should, of course, be chosen for this number. Nevertheless, unaccompanied choral singing is seldom undertaken without the tone becoming flat before the end. It might be a good thing, if it can be remembered, to give the right pitch from time to time from the wings.
Richard Wagner
Source: Letters of Richard Wagner, Volume 1, ed. Altmann/Hull (London: Dent, 1927), No. 61