The first and second levels mentioned here are the progressions of chords. There are seven levels of chords, namely first-level chords, second-level chords, third-level chords, fourth-level chords, fifth-level chords, and sixth-level chords. , seventh degree chord. And Wuqijia is a fifth-level chord (dominant chord) and has a brother that is a fifth-level seventh chord (dominant seventh chord), and the fifth-level seventh-level chord is divided into categories A and B, so there are five-seventh-level chords and The five-seven-B chord! It’s not the piano progression mentioned on the first floor!