They just elongated each measure by its same amount so we had harmony changing on each measure, and then in that middle section each chord was changing at the rate of two measures.

但它的基本形式没有改变，而在每个小节中和声都发生了改变，接着在中间的乐节，每个和弦每两小节改变一次。

耶鲁公开课 - 聆听音乐课程节选