The serious artist is one who is up to the elbows in the stuff of God's world. (pg 68: Performer as Priest and Prophet).
I've mentioned this book on more than one occasion in this blog, and may well do again before I've finished reading it. In the chapter I've just read the authors talk about Schoenberg's unfinished opera, Moses and Aaron, in which the composer sees Moses as the creative artist, and Aaron as the interpreter - for good or bad. (In Aaron's case, quite often bad.)
It's an interesting approach to the story, and possibly not one with which everyone will agree. Composers need performers - unless, of course, like Stockhausen and some others, they cut out the performing 'middlemen' and do everything themselves. Some composers are performers - yours truly, for one - and can be counted on to interpret their own music according to the composer's wishes. Except that I find I play my own pieces differently every time I touch them. Does that make me a 'good' interpreter or not? I'm always hearing that such and such an artist was a consummate interpreter of Mozart, Bach or Brahms (as the case might be); but what does that actually mean? That they played the pieces so wonderfully that everybody thinks that's how they should be played?
For a time Wanda Landowska was considered to be the epitome in terms of interpreting Bach. Then along came Glenn Gould, and everybody thought he was the epitome in terms of interpreting Bach. And, of course, he's now been supplanted by someone else.
So were those earlier interpreters interpreting wrongly? Don't think so. To me a piece of music is like the script of a play. Yes, there are certain things you must do: play all the notes, aim to be consistent with the composer's intentions in terms of dynamics, make sure that you have a good idea of what style such a piece might be played in. But that's pretty much where it all ends. After that, you're the performer (rather than the 'interpreter') and you present to the listeners the piece of music. You're a conduit between the composer and the audience, but you're not a conduit that brings nothing of yourself to the piece. If you can keep yourself out of the way you'll be doing extraordinarily well, I think.