You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
Frédéric_Chopin

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?

21