John Williams is one to the most famous movie composers of our time. Were you surprised to learn that much of his music is based on previously

John Williams is one to the most famous movie composers of our time. Were you surprised to learn that much of his music is based on previously composed works? In Star Wars Williams gives each character their own theme. What opera composer used a similar technique and what is it called? What instruments are used for the heroic theme? What instruments are used for Princess Leia's theme? If you have seen the movies, do you think the music fits with the characters?