Over the course of the last few decades, the definition of what constitutes “classical music” has gradually been changing.
When I was a child, “classical music” was pretty strictly defined as art music for its own sake — or perhaps as a companion piece to another medium that was also defined as fine art, such as ballet or opera. Soundtracks, of course, existed, but despite sharing a lot in common with “classical music” as defined by popular culture at the time, they were regarded as something… if not lesser as such, certainly different.
Whizz forward to today, however, and we have established classical musicians putting out albums that consist entirely of video game music. Who’d have thought it?