According to the principle of acoustics: each accurate musical tone has its fixed vibration frequency, if each played tone conforms to a specific vibration frequency, then these tones are accurate, otherwise they are inaccurate. Erhu is a musical instrument with no fixed pitch, because the height and method of pitching vary in different pieces of music? For example: "Erquan Reflecting the Moon", "Jianghe Water", "Thinking About the Great Wall" and "Tan Music", etc.) Therefore, in addition to the general standard, the pitch of the tone in the performance also depends on the different modes, tonality, and different musical styles and charms in the music. It can be said that the pitches of all the intervals of the sound in erhu performance are relative.

The erhu is a national stringed instrument mixed with various temperaments. Since it has neither a fingerboard nor any fixed grade, it is quite difficult to control the pitch. Even a very experienced player, without long and effective practice, can find it difficult to play a series of fast and accurate notes easily and confidently as needed. This is because: in addition to the grasp of left-hand pressing and changing the handle, the most important thing in pitch control is the accuracy of auditory analysis and judgment of pitch. Most people are accustomed to think that "inaccurate pitch" is mostly caused by the unskilled position of the left hand or the movement of changing the handle. In fact, the reasons for the inaccuracy of playing the middle pitch are firstly the dullness of hearing and the lack of stability for accurate pitch." foreshadowing" (ie: "thinking ahead"). A player who has a very keen sense of pitch and (hearing) will often subconsciously feel uncomfortable or even stimulated when he hears inaccurate tones in his own or someone else's performance. At this time, the player with a keen sense of hearing will subconsciously adjust the pressing position of his left hand until the pitch is reached. This fully demonstrates the important role of hearing in controlling pitch and adjusting the position of the sound. For this reason, in the process of training students to control pitch, they should first train their acuity of hearing through instruments with fixed pitches such as piano, electronic organ, accordion, etc. The ability to hear the sound first ("inner hearing") in the mind before pressing the sound. Then, through different levels of scales, arpeggios and other exercises to adjust and stabilize the position of his (her) left hand pressing the notes and the accurate change of the scale. For players with less acute hearing, the process of identifying and controlling intonation is also a relatively difficult training process. In this process, the performer must concentrate his attention (hearing) highly from beginning to end, and sometimes even repeatedly train the sense of the exact position of the notes on a note-by-note basis to cultivate and stabilize his tactile memory and distinguish between different pitches auditory memory. Only in this way can we train the ability to listen to the pitch well and master the accuracy of pressing the sound and changing the handle step by step.

I think that the intonation training in erhu performance should be based on the twelve equal temperament, because only if you are familiar with and master the twelve equal temperament can you adapt to the frequent inversions, off-tones and complex scale structures in many pieces of music, and also be able to perform more widely music content. Taking the twelve equal temperament as the basis does not mean that it excludes the combination of the fifth and pure temperament, which is inherent in the erhu performance. At the same time, in the practice of scales, arpeggios, etc. and the performance of music, not only should the performer realize the relative pitch of each note in different modes and different scale structures, but also teach him (she) to be proficient. To master the pitch tendency of the third and seventh grades according to the sound. Only in this way will the clarity and stability of the melody be more prominent in the performance, and the hearing will be more satisfying. In some national modes, the neutral tones of the fourth and seventh, that is, high and low, are very distinctive and charming in performance, such as "bitter" and "happy" in the Shaanxi music style, and in the Cantonese music style. The "Yi Fan Xian" and so on. When playing music of these musical styles, you should press the tone according to the pitch requirements of neutral tones to highlight the unique style and charm of the music; The use of special pressing techniques such as "chanting" and "kneading" based on pressing and kneading can also highlight the rhythm characteristics of the music, making the music more unique and flavorful.

To sum up, the problem of intonation in erhu performance is very important and extremely complicated. It is the lifeblood of playing and an important premise. If a player can't even press the notes accurately, then no matter how skilled he or she is and how passionate the performance of the music, such performance will be meaningless.