It's simply material found on page fifteen of your textbook but let's review it. We say this is a beginning course so we assume no previous knowledge.

这是你们教材十五页上的一些简单材料,我们复习一下,我们说这是个入门课程,所以假设之前你们没有任何相关知识

耶鲁公开课 - 聆听音乐课程节选