In Mixed Opinions and Maxims, Nietzsche pictures how Beethoven might have reacted to contemporary performances of his music. He is, of course, talking about Beethoven circa 1878, the Beethoven of Wagner and Hans von Bülow, but his remarks seem no less relevant to the Beethoven of today:
We honor the great artists of the past less by the barren awe that leaves every word, every note lying where it was placed than by active efforts at helping them come back to life again and again. — To be sure: if we were to imagine Beethoven suddenly coming back to life and being confronted by one of his works resounding with the most modern animation and the refinement of nerves that serve the fame of our masters of execution: he would probably remain for a long time silent, uncertain whether he should raise his hand to curse or to praise, but perhaps finally say: "Well, well! That is neither I nor not-I, but some third thing — yet it seems to me right enough, even if it is not exactly right. But you might want to watch what you are doing, because you are in any case the ones who have to listen to it — and the living are right, as our Schiller says. So be right, then, and let me descend once again."
I quote from the new translation by Gary Handwerk, part of Stanford University Press's slowly unfurling edition of the complete Nietzsche in English. You can read the original German here, on the comprehensive site Nietzsche Source. "Das ist weder Ich noch Nicht-Ich, sondern etwas Drittes" — every composer must have thought so more than once.
