qnli question: What form does Temperley feel that Chopin's ballades and scherzos are based on? sentence: Temperley opines that these works, which contain "immense variety of mood, thematic material and structural detail", are based on an extended "departure and return" form; "the more the middle section is extended, and the further it departs in key, mood and theme, from the opening idea, the more important and dramatic is the reprise when it at last comes."