You know, that's a great discussion to have at another time.

Is it growing exponentially? Personally, I'd say that changes at the margin are becoming smaller. I think that the difference between 1940-1980 is much greater than 1980-2020.

As an aside, it's funny how static music has been for years. There are numerous bands that sound like they would have been reasonably successful in 1970 (and visa versa). 1920 vs 1970 is a whole 'nother issue.