How did george gershwin and leonard bernstein both straddle the worlds of classical and popular music?

They were both classically trained, but used their training to try new compositions and use brass for swing and jazz as well as broadway!

The gregorian chant was a major cultural milestone in the middle ages. it was one of the first codified forms of music meant to be played as written, where previously it was difficult to mass-produce and disseminate any music. what's more, these chants were also some of the first examples of musical notation: the notes and bars of today's music sheets are a reflection of centuries of evolution beginning with these chants. it became official throughout the entirety of the catholic church, meaning that nearly all of europe followed this musical notation and styling.