1. Music system

Music system is the sum of sounds with fixed pitches used in music. This is the result of people's long-term development in music practice.

2. Sound sequence

The sounds in the music system are arranged in ascending or descending order, which is the sound sequence.

3. Sound level

Each sound in the music system is a sound level.

The seven sound levels with independent names in the music system are the basic sound levels.

Raising or lowering the basic pitch level is changing the pitch level. Increases are marked with "#"; decreases are marked with "b"; re-rises are marked with "X"; re-falls are marked with "bb".

4. Sound groups

The fifty-two white keys on the piano repeatedly repeat the names of the seven basic tone levels. In order to distinguish sounds with the same sound name but different pitches, people divide the sound sequence into several groups. The group in the center of the sound column is called a group of small characters, and the sound level is marked with English lowercase letters and the number 1 above it, such as. c1d1e1...the ones higher than the small character group are called the small character group 2, the small character group 3, the small character group 4, and the small character group 5. The ones lower than the group of small characters are called the group of small characters, the group of large characters (marked by English capital letters), the group of large characters (marked by numbers on the lower right of the capital letters, such as C1D1E1...), and the second group of large characters.