Athens was a commercial democracy with a popular culture that is now the highest of high cultures.Yes, that is actually true. In ancient Athens the theater festival that the plays of Sophocles and Aeschylus and Aristophanes were written for was immensely popular, attended by every citizen. It was the equivalent of major league basefall, football and Broadway all rolled into one. Of course, since this was before the Internet and television, there was nothing else to do!
The point I want to make is that one era's popular culture can become another era's high culture. What makes this possible? I think the main thing is the aesthetic quality of the work. The Greek playwrights are the high culture of our day because their plays are simply great plays. The music of Bach is the high culture of our day because it is great music. In its own day it was not exactly popular. Most citizens of Leipzig probably thought of his music as being pretty good church music if nothing else. What turned it into high culture was not that it had a harpsichord part but the high aesthetic quality.
What are some other candidates for popular culture becoming high culture? How about this rather naughty catch (round) by Henry Purcell, entitled "So kiss my arse":
There is a canon by Mozart that is even more obscene. But the point is just that, in the 16th and 17th centuries, there was a lot of primarily vocal music that was very, very popular. If there had been the mass media that we have today, it might have been as popular as our pop music. Today we classify all this music as "classical".
Other examples I might mention would be the music salons very popular in most European capitals in the 19th century. In Vienna you could have heard Franz Schubert trying out some new lieder:
The big virtuosos were also hugely popular. Franz Liszt toured Europe playing his own music and transcriptions of things like Beethoven symphonies and Schubert lieder:
And Paganini, after many years of preparation, swept Europe like a storm:
All of this "classical" music is charming, entertaining and mostly simple enough to be enjoyed by mass audiences.
But probably the most popular musical form in the 19th century was the opera:
Now, opera is regarded as "high culture" but during the 19th century it was popular culture.
The interesting thing here seems to be that what transformed everything from then to now, is technology. Not just technology, of course, but technology had a lot to do with it. What replaced opera was the movies and television. Now, instead of watching Turandot in the opera house, we watch Breaking Bad at home.
Of course the whole aesthetic content is different as are the cultural values expressed.
The thought occurs to me that it is entirely likely that, before Beethoven, no composer wrote for "history" or "high culture" at all. They wrote for the immediate needs of the immediate audience. This is as true of a Haydn symphony or string quartet as it is of a Mozart piano concerto.