Significant Pieces of Music
Listen to Mozart's Symphony No. 40:
Listen to Beethoven's "Für Elise":
The story behind the following Haydn example is interesting. As you listen, imagine the Esterházy family’s reaction. Haydn was disturbed at the rudeness of his patron’s attention (or lack there of) during his performances so he composed a very quiet piece that had a startling sudden loud note in order to get them to stop talking and listen.
Listen to Haydn's Symphony No. 94 "Surprise Symphony":