What a piece of (classical) music is remains a problematical consideration. Does the "music" exist as the score written by the composer? Or, is music rather something that must be heard to be real? And, interpreting a score brings up issues of difference and change so much so that every performance of a written score will be different from every other one. Recording certainly solidifies a performance, but is that really what the music is if what is there on the recording differs from what is there on another recording or in the next live performance of the piece? Though the "music" of the score doesn't change, the "music" of the various performances will be various. So what are we left with?
In some sense we can only cherish a work of music by way of its performance, which can render it pleasing or non-pleasing, invigorating or discouraging, lovely or ugly …. Yet, I grimace at that very remark having spent time studying Bach scores on the page and appreciating the wonders and beauties of intervals, harmonies, and technical nuances of compositional construction -- all without ever actually hearing a performance (outside of what I hear in my head). Too, I know I can be deeply moved by staring at notes on a score page, as I can be deeply moved by the sounds flowing from a symphony orchestra, an instrumental soloist, or from my stereo speakers.
If I do hear a piece of music in my head, is that real? I can imagine unicorns and purple spacemen, too.
I have thousands of records and CDs. (Yes, I'm one of those folks -- but you all know that already!) Do I possess these discs as music? In other words, can I hold Beethoven's nine symphonies in my hand, or is the music only rendered when the needle is set to the groove or the machine translates 0s and 1s into sound waves?
What exactly music is boggles me enough that the initial question of this thread seems distant. I often wonder what exactly I am hearing when I experience, say, the Mahler 2nd. I can only ever hear a single moment of the music, so how is it that I somehow comprehend this giant work as a unit? If my memory completely collapses, will my appreciation of music end with it? Does hearing a musical work as a unit depend on memory at all? How is it that I can comprehend a theme when I can only ever hear the slightest, smallest moment of it at any given time? At least when I looking at the score I can take the piece in as I would a painting or sculpture -- in a kind of "single vision".
This is all mysterious to me. Which perhaps explains why I continue on exploring music. I've always loved a good mystery.