I must admit that regarding LB I risk being somewhat biased... I am madly in love with him and I am often willing to forgive things that I wouldn't even forgive myself. That said, particularly regarding Mahler (but not only), I find that his readings (and the arguments he brings in support of them) are on the verge of being incomparable, due to the depth and penetration of the most intimate, violent, and contrasting meanings of the Mahlerian language, which perhaps Bernstein understood like few others, while approaching it, in his own way, with a very identifiable personality. In an attempt to be as objective as possible (which, as I was telling you, is quite complicated for me in LB's case), I would say that the exuberance of this great musician (I am speaking of Bernstein) pairs well with a language—that of Mahler—which is made of such contrasts, such excesses at times, that they need to "be brought out," to be exaggerated and not smoothed over.
Today perhaps, after a century of Mahler (but let's not forget that the first complete Mahlerian cycle in Italy was Claudio Abbado's at La Scala at the end of the '60s, incredible but true...); I was saying, after a century of Mahler we have, both musicians and listeners, acquired a familiarity that was certainly almost a utopia in Bernstein's time. Memorable is his performance with the Vienna Philharmonic (for whom, among other things, those symphonies were written) with Bernstein forced to sweat blood in front of a recalcitrant orchestra that refused to play that "shitty music" (their words, quoted by LB himself). Mahler said that "everything is written in the score except the essential," and I think Bernstein was able to bring out exactly that essential.
A totally different approach to his music, which I appreciate very much even if what I have just said may seem strange, is that of Pierre Boulez, who reaches very high results in Mahler's music, in my opinion, starting from a completely different angle. Bernstein emphasizes the emotional aspect of that music, using everything possible from the scores that "serves the purpose," while Boulez emphasizes the meticulous construction of the scores, especially the play of colors, cleaning and refining the palette so that all that Mahler wrote is rendered with maximum fidelity (and, I must say, he succeeds like few others). At that point, the "essential" emerges with a power completely different from that unleashed by Bernstein's readings, because in Boulez's readings the essential seems to explode directly from the written page, to which the French conductor reserves a respect that I find only in some conductors who deal with the Baroque repertoire.
This, in my opinion, confirms something that I continue to find exhilarating in making music: the text, the author, are the starting point, the one and only. Never, ever should a musician put themselves ahead of the music they interpret. Nevertheless, the results can be so surprisingly different as to eliminate any concern about loss of variety or loss of fantasy in following a written text which, due to the type of language it uses, is among the most "interpretable" of all. In fact: as Brendel says, much more fantasy is required if one seeks to be faithful to a composer than if one takes too many liberties, because arbitrariness can be poorly masked as fantasy, whereas a lack of fantasy is and remains just that.
