Context: The 21 nocturnes are more structured, and of greater emotional depth, than those of Field (whom Chopin met in 1833). Many of the Chopin nocturnes have middle sections marked by agitated expression (and often making very difficult demands on the performer) which heightens their dramatic character.

Question: How many nocturnes did Chopin compose?
Answer: 21

Question: What is it about the middle of Chopin's nocturnes that increases their drama?
Answer: agitated expression

Question: Chopin's nocturnes were more structured than who?
Answer: Field

Question: What year did Chopin meet Field?
Answer: 1833

Question: Which type of Chopin's compositons were difficult for perfomers due to their middle sections?
Answer: nocturnes