Quick bow is a difficult movement in erhu skills, and it is a difficulty in the basic skills of erhu. In erhu textbooks and articles on Kuaigong, we often see references to the graininess of Kuaigong. However, a specific explanation of the concept of Kuaibong granularity is rarely involved.

Usually the requirements for the effect of the fast bow are: clear and full pronunciation, clean and agile, equal time value, no traces when changing strings and handles, and granularity. Clear and full means that the string is rubbed tightly, with strength, and the pronunciation is firm and not empty; clean and agile means that the two hands cooperate closely and not sloppy; the time value is equal and no traces are revealed, which refers to the control of the distance between the bow and the string. Left-handed technical requirements. Textbooks before the 1980s said this. But these formulations are not enough to visualize the essential characteristics of the fast bow, so the formulation of "granularity" appeared later.

Although there is no clear definition of Kuaibong granularity, the formulation of granularity reflects the essential characteristics of Kuaibong. As the name implies, the so-called granularity is the pronunciation of the fast bow. Each note is like a "grain", which is firm, clear and neat like a grain, and each grain is the same size. This image statement succinctly summarizes the phonological characteristics of Kuaigong, so it is gradually accepted by everyone, and has also been recognized by erhu experts. Many experts have written granularity into teaching materials, and regard granularity as a technical requirement for fast bows, and many people also take granularity as a sign to measure the quality of fast bows. The information at hand is incomplete, and the earliest source of the formulation of granularity cannot be verified for the time being, but this does not affect our in-depth discussion of granularity.