How does knowing about a piece's themes and their interaction of the orchestra deepen our understanding of the piece

To be able to communicate with the audience and tell them whats going on in the piece.  So using all of the dynamics to make it sound realistic and make the audience and anyone listens fell like something real is going on...

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.