More generally, “define classical” has always been a problem, and the approach has always been a “you’ll know it when you see it” kind of view. It’s very hard to put clear limits to it.
Is this classical?
- A recording of some Mozart symphonies
- A recording of Medieval music and plainchant
- A recording of contemporary art music, like Glass or Reich
- A recording of Keith Emerson’s Piano Concerto (originally released in an EL&P album)
- A recording of Beatles arrangements by an orchestra
- A recording of classical arrangements by a rock band
IMO the answer is yes to all but the last of them, but it’s hard to explain why. @CallerNo6 had worded this at some point as “it’s classical if it’s recorded or presented in a classical context”, which I generally agree with as an idea but it’s hard to explain properly to people.