Simplify the following text for a Grade 5 native English-speaking person.
Original: C minor has been associated with heroic struggle since Beethoven 's time , with the quintessential work in the key being his Symphony No. 5 ; see Beethoven and C minor .
Simplified: C minor has had the meaning of heroic struggle from Beethoven 's time . One of the most famous pieces in this key is his Symphony No. 5 .