In the major and minor key system, levels I, III, and V are all stable levels. Except for these three levels, they are all unstable levels.

In the major and minor key system, levels I, III, and V play a stabilizing role. The degree of stability of these three stable sound levels is different. Level I is the most stable, while levels III and V are less stable.

The three stable tones and their stability can only be displayed when they sound with the tonic triad. If other non-tonic triads are used, they will not be stable. Level II, Level IV, Level VI, and Level VII are unstable sound levels. Under appropriate conditions, they show the tendency of the second-degree relationship to become stable sound.

Extended information

Major mode and minor mode. A mode composed of seven tones is called a major mode, in which the stable tones combine to form a major triad. The minor mode is also composed of seven tones, of which the stable tones combine to form a minor triad.

The tonic of the major mode and the third note above it are the major third, because this interval best illustrates the color of the major mode. The tonic of the minor mode and the third note above it are minor thirds, because this interval best illustrates the color of the minor mode.

In music, stable tones often appear on the strong beat of a measure and at the end of a phrase or section to obtain a sense of stability in the music segment; long tones of more than two beats are often played by stable tones.

The roll call 2467 in the major mode is an unstable tone, and its usage is very different from the stable tone, except that the major key is the supporting tone of the music. Unstable sounds have a strong sense of movement and always tend to move toward nearby stable sounds until they move to stable sounds.