Chord refers to a group of sounds with a certain interval relationship. Three or more sounds are vertically combined according to the relationship of three-degree superposition, which becomes a chord. !

In pop music, small three and small two are the main ones, and seven and small seven are also commonly used. Adding chords is also very common, especially add9, and subtracting chords are sometimes encountered. The sixth chord, minor sixth chord and ninth chord are rarely used.