“Trying to define “classical music” in a short phrase (or a few sentences) is a forlorn task. The very attempt is the product of an outmoded and insupportable theory of definition. To cut a long story short, you might want to have a look at my online essay, “Definitions, Dictionaries, and Meanings”, at http://www.sfu.ca/ph…definitions.htm . As the last half-century of philosophical research in the area shows, just about everything taught to children in the public schools about definition (yes, this almost certainly includes you) is simply untenable and false.
There is, and can be, no neat definition of “classical music” any more than there can be a neat, capsule, definition of such concepts as “cause”, “justice”, “lemon” [see section 8 and subsections in my aforementioned essay], “science”, “religion”, etc. (ETC.!)
If you want to explain to another person what you mean by “classical music”, proceed by offering examples (instances, exemplars, etc.) If, in your use of the phrase, you include folk songs, say so; if you exclude folk songs, say so. And let it go at that. Don’t assume that there is any one, more or less, universally agreed-upon, ‘correct’ view. And even if there were, so what? What, of import, could possibly hang on such a resolution? Just simply try your best to inform others what sub-genres of music you’re keen to discuss and then get on with it. I don’t have the book at home in front of me, but one does well to recall Karl Popper’s admonition (in Conjectures and Refutations) to avoid trying to define one’s terms.” (source)