What two significant historical occurrences advanced the development of music in the nineteenth century? explain how each had an impact on music and society?

There were many historical occurrences in the 19th century that have cast a large influence on music and all other arts.
The first one could be the awakening of the middle class in society. Up until 19th century, composers couldn't make it on their own. Their audience was mostly comprised of aristocrats. The upper classes, coming from nobility and church, were their benefactors and patrons. Composers often worked either as kapellmeisters in churches (like Bach) or court musicians (like Lully). The 19th century was the first time that they gained relative autonomy and wider audience among the bourgeoisie, that is the middle class. The 19th-century audience was also the first one to see large concerts in concert halls as we know them today (instead of at the court or in the church).
The second occurrence is the political upheaval all over Europe around 1848. It was the rise of national states and patriotism, which was perceived as the quest for freedom and re-establishing national pride. That is when Romanticism came to its highest point.