Task: Question Generation
Input (English): J. Barrie Jones suggests that "amongst the works that Chopin intended for concert use, the four ballades and four scherzos stand supreme", and adds that "the Barcarolle Op. 60 stands apart as an example of Chopin's rich harmonic palette coupled with an Italianate warmth of melody." 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."
Output (English): What form does Temperley feel that Chopin's ballades and scherzos are based on?