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:
Chopin's polonaises show a marked advance on those of his Polish predecessors in the form (who included his teachers Zywny and Elsner). As with the traditional polonaise, Chopin's works are in triple time and typically display a martial rhythm in their melodies, accompaniments and cadences. Unlike most of their precursors, they also require a formidable playing technique.

Question:
Chopin's polonaises needed what kind of playing technique?

formidable