All pure intervals, major intervals, minor intervals and fourth and fifth intervals are called natural intervals. All increases and decreases, except the doubling and subtraction interval of adding four and subtracting five, are called variable intervals.

Raising the upper voice or lowering the lower voice of an interval can increase the number of tones of the interval, lower the upper voice or raising the lower voice, and reduce the number of tones of the interval.

Strong beat and weak beat with the same time value appear periodically, which is called beat. The symbol used to indicate the beat category is called the time signature.

Single beat refers to a beat with only one strong beat, which can be divided into strong beat and weak beat. Duplicate beat is a beat composed of two or more different types of single beats with the same unit beat value, which increases the beat points compared with single beats. A beat composed of two or more different types of single beats with the same unit beat value is called a mixed beat.

Tones with the same or different lengths are regularly combined together, which is called rhythm. Mainly refers to the combination of long and short sounds. Beat mainly refers to the alternating law of sound intensity.

A sound starts from the weak beat and continues to the place behind the strong sound, which breaks the normal law of strength and reverses the original relationship between strength and weakness. This sound form is called syncopation.