(Note: This post has been updated (2) as of 9:58 PM Eastern on 3 Feb. See below.)
Ms. Hirsch voices her opinion that there's "much genius in the massing [in Wagner's music], and yet there's also genius in the counterpoint," with which opinion I agree wholeheartedly. Wagner, in both harmonic invention and contrapuntal construction, is the logical successor to the great Bach himself. But the contrapuntal genius of that greatest of contrapuntists is also revealed in the massing; i.e., in the gestalt effect of the interlacing of the music's multiple contrapuntal lines. Hearing the individual lines as individual lines may be instructive and a source of wonder, and the individual lines in themselves beautiful, but it's in the summed product of their interlacing that their and Bach's genius is made manifest.
Just so with the music of his logical successor who better than anyone knew that the genius of his own counterpoint was revealed in the massing, and so took extraordinary care in his orchestrations to force it to be so heard. Any interpreter who attempts to defeat Wagner on that point is doing him, and, more importantly, the music a gross disservice, not to mention the gross disservice done to audiences for that music.
Ms. Hirsch then writes:
I have not yet been to Bayreuth, and it sounds as though ACD has been, so I am interested in hearing more about the "circle-squaring" aspects of achieving transparency in that theater. My experience is strictly with performances recorded there, in which, of course, transparency may be achieved by the clever placement of the microphones.
As Ms. Hirsch correctly conjectures, I have heard Wagner in the Festspielhaus, and, briefly, the combined effect of the sunken orchestra pit and the auditorium's "non-analytic" acoustic is to blend the orchestral sound in such a way as to almost force a hearing of it in the massing; precisely Wagner's intent, as I've already stated. Any imagined transparency heard in the house is a direct result of Wagner's purposeful orchestration to achieve that effect. Criminals such as Norrington and Boulez may mess with the orchestral textures in ways Wagner never intended or even imagined in order to force transparency where none was written, but in the Festspielhaus their efforts will go largely for naught except to make the orchestra sound anemic in comparison with what one expects to hear from it in that auditorium.
Finally, as to singers, I agree with Ms. Hirsch that Nilsson's voice is quite "steely," and lacks the plush, lyrical quality of, say, a Flagstad or Varnay. But Nilsson's voice has its own kind of beauty, perfect for the Ring's Brünnhildes though less perfect for, say, Tristan's Isolde. Judging Nilsson's voice in Wagner by how it executes trills and written-out ornament, however, is a bit silly given that the trills and written-out ornament in Wagner's mature works are, as I've said, just this side of nonexistent they're so rare. If one want to hear trills and ornament in the vocal line, I suggest he try Baroque opera, or the operas of the Italian bel canto masters rather than those of Wagner who had little use for such peacock embellishment.
Update (5:49 AM Eastern on 1 Feb): Lisa Hirsch responds.
Update (9:58 PM Eastern on 3 Feb): For the ongoing, um, conversation on this, see here.