i think it's pragmatically real to actually hear something like the Busch quartet's recordings and have that tell you that there was a different sound at the time. just as a pre-war steinway's sound was sweeter and less analytic -- not more shoddily made or anything, just made for a different aesthetic.
i'm a composer, by the way, so all you say about interpretation is trivial -- basic to the understanding: that the problem with having your music performed is that it's performed by players with personalities of their own. sometimes that's as good for the composer as learning how a violist actually fingers.
but, what i'm getting at is that we've got this big music now, in huge auditoriums and stadiums, and what are people actually receiving as music? i think they're getting a Hammond organ experience, that gut-thumping swoon so beloved by drunks and losers.
today is now, but so is my understanding of how music is noise bent into melody. melody is everything, even in webern.