[...] They are rehearsing Tannhäuser at the Opera with a zeal, earnestness, exactitude and care which is the very pattern—unattainable I have always thought—of what such study should be. I have never seen anything even approaching this punctilious and minute attention to detail at any theatre. My German singer, Niemann, is rubbing his eyes and confessing that he is learning his score for the first time. Besides the uncommon excellence of the organisation of the Opera as a whole, I must particularly praise the extraordinary personal ability of the chief officials and, above all, the inestimable directeur du chant who practises the singers at the pianoforte. All the technical side of rehearsal is managed with incomparable accuracy and neatness, the slightest divergences of text reconciled, etc. [...]
Source: Letters of Richard Wagner, Vol. 2, selected and ed. Wilhelm Altmann, trans. M. M. Bozman (J. M. Dent & Sons, 1927), No. 478