[...] I learn that Herr Vogl has drawn your attention to certain difficulties which will arise in regard to the proposed performances of Parsifal in Bayreuth if I do not very definitely give himself and his wife first place in the company. This decides me to ask you to convey the following in my name to these excellent artistes. Herr Vogl himself knows that, slowly but ultimately very definitely, I came to recognise his great merits. If I am to allot the primacy among five singers I would cordially grant it to him. As regards Frau Vogl, much as she has moved me in the various rôles in which I have heard her, I felt it best not to offer her the part of Kundry, as I need for this part a vocal vigour which I felt I could not expect from this singer. Accordingly I originally allotted the part to be sung alternately by Frau Materna and Fräulein Brandt, and it was only when I thought I saw that Herr Vogl might feel concerned in the arrangement that I left it to his own judgment, after experience of the matter, to give his wife a share in this rôle. As a manifesto of mine will have informed Herr Vogl that I propose to draw on a supply of talented singers to study for the numerous performances of Parsifal, he will, once he enters into my idea, not feel offended if he sees Herr Gudehus and Herr Jaeger take the part of Parsifal in a few performances in addition to Herr Winkelmann, who is appointed to alternate with him. In the same way Fräulein Malten will sing Kundry a few times, and I should feel well satisfied if Frau Vogl would take part in several of the very numerous performances. I may say that Frau Materna believed she was in actual possession of the part as my first invitation was to her, and now makes it a condition of her co-operation that she should sing it at the first performance, while Fräulein Brandt, who has already studied Kundry with me for seven months to my very great satisfaction, will, I understand, modestly renounce the privilege.
Foreseeing these few difficulties, I still believed we could wait to settle them till we were all met together, but Herr Vogl's declaration to you shows me that I must take my decision betimes, and I will inform you of it as follows: I am ready if necessary to cut down the number of performances advertised so drastically as to be able to manage with one single personnel, so long as that personnel is thoroughly friendly and willing to enter into my ideas; in that case I should have to be willing to put up with the secession of such artistes as were unable to maintain this concord with me.
Consequently I have to ask you, my dear friend, to acquaint Herr Vogl in my name with what I have said here, at the same time requesting him to let you know as soon as possible whether I am to make the suggested alterations in the advertisements of our Dramatic Festival or not. [...]
Source: Letters of Richard Wagner, Vol. 2, selected and ed. Wilhelm Altmann, trans. M. M. Bozman (J. M. Dent & Sons, 1927), No. 734