What's a piece of classical music that everyone knows but most people don't know they know?

https://lemm.ee/post/16495915

What's a piece of classical music that everyone knows but most people don't know they know? - lemm.ee

Rhapsody in blue.

Bits and pieces of it have been used in all sorts of places. The story behind it is fascinating.

The TLDR, the guy putting on the concert asked Gershwin to write a jazz fusion piece, Gershwin declined. Then the guy put out promotional material anyway saying that Gershwin was premiering a new piece.

Some back and forth, and Gershwin wrote a masterpiece in less than 5 weeks.

Rhapsody In Blue: Gershwin

YouTube
is that considered classical?

1920s orchestral jazz fusion. I'd say it counts. Especially since it's classic jazz, not the more modern jazz that people are familiar with.

It hits all those classical notes and takes them a step further. It's also a true masterpiece. Which gives it even more leeway.

yeah this sent me down a wikipedia rabbit hole and I found that classical music has a classical period but like the period right before most people would definately think of classical. I think with my head I saw classical and thought old classical was what was meant. Like behtoven and bach and such.
Purists would tell you Bach is baroque, not classical, which while technically true doesn’t really cover the modern use of the term classical music.