Instruments were less reliable in the domantic period then they were during the renaissance period

Nationalism is a strong identification with a particular political group, often an ethnic group. Nationalism is often accompanied by a strong sense of pride and connection with one's particular group. 

This nationalism often found its way into the music of the period. Composers increasingly used elements in the music that were related to their national heritages. For example, many of the operas written during this period relate the histories of particular ethnic groups or nations. Some composers adopted melodies and other musical elements that were common in the folk music of a country.