Authenticity is a problematic concept when it comes to all art. In the world of classical music, the problem is especially important to address because most of what we do as musicians is reproduce the music of others. We don't typically own, at least in a strictly philosophical sense, intellectual property over our performances, since they're written by someone else. Unfortunately, as the classical music scene struggles with evolving standards of intellectual property involving the internet and duplication, it simultaneously struggles to evolve out of an antiquated and damaging mindset involving all that music in the public domain!
It's one of those things that, if you operate outside the world of classical musical performance, you'll probably say either "huh?" or "who cares?!", and maybe you're not totally wrong. But maybe you would care more if the world of classical music performance weren't so bogged down in its silly performance practices!
Before writing anything more witty about it, I feel I have to lay down the groundwork for what I want to say. Really, it's one of those things that doesn't fit into a blog. But what am I gonna do.
The general attitude among people who play and teach music is that the music of the past is so sacred, so untouchable, that to a greater or lesser degree it should always be reproduced in the manner that best mimics its original conception, that is, however the composer actually envisioned the music being played at the time he or she wrote it.
This general attitude, though, fails on all sorts of levels. First off, it's clearly impossible in practice to determine how a composer conceived of his own music when the composer is dead. The incomplete record left behind by dead composers is far from sufficient for such a task, even for the best scholars (who are most often asking entirely the wrong questions anyway), and in the end, we can't read dead people's minds. Even when we have access to a composer's recording of his own music, the idea that a performance is identical to a conception is, as any artist knows, far from the truth. Anyone who thinks he knows much about what a composer "intended" for his music is usually trying, unconsciously or otherwise, to justify and confirm his own biases.
Epistemologically, it is also in principle impossible to have any idea how a composer conceives of his music. Even if we did have ready access to his thoughts, who's to say they are even stable over time? What do you do if the composer had one picture of his music when he first started writing a piece, another when he finished, and a completely different one for the very same notes, years later? And that's just to consider a composer's lifetime. Who's to say what Mozart would think about his music today, after hearing it over and over, thousands of times? Who's to say what he would have thought about it, after seeing the course of Western music, and the changes wrought upon it by subsequent musicians? Clearly, we can only speculate.
In the end, even if we could summon Mozart from the dead, have him listen to 2 centuries worth of music and performances, and ask him, "how should I play this sonata?", should I be bound by his answer? No! The purpose of music isn't to shackle our own creativity, but to unleash it. Our only goal should be to make the best music possible, whatever Mozart tells us.
Great musicians have thought otherwise. But they're wrong. Even the performer who, for me, best reflects what I've written above—Glenn Gould—preached a different story altogether. He often cited the intentions of the composer as his highest authority while playing standard repertoire in a way that no one had even imagined it could be played. Clearly, his highest authority in performance was himself, and aren't we all lucky for that?