We are going to be employing chords all in the course of this chapter, Therefore if you must, you should refer back to Chapter three and Chapter 4 on chords and switching involving them.知乎，让每一次点击都充满意义 —— 欢迎来到知乎，发现问题背后的世界。...Smoke within the H2o by Deep Purple - An ultra-common riff