Suzhou erhu comes in many varieties, mainly due to differences in materials used, the shape of the sound box, and the carving on the head of the instrument.
Suzhou erhu has a wide variety of types and designs, which mainly differ based on their materials, the shape of the sound box, and the carving on the head of the instrument. For example, there are commonly seen rosewood curved-neck erhu, rosewood dragon-head erhu, padauk curved-neck erhu, and ash wood flat-top erhu. There are also other types such as the erhu with amplification chamber and the erhu with support base. Since the 1970s, China's musical instrument makers, scientists, and performers have carried out a series of reforms on the erhu, leading to the emergence of new varieties such as the flat round sound box, flat hexagonal sound box, flat octagonal sound box, two equal-sided hexagonal sound box, straight-edged egg-shaped sound box, and elliptical sound box erhus.
The flat round sound box erhu was successfully developed in the early 1970s. Based on the acoustic principle of the elliptical speaker, it changed the hexahedron resonator into an ellipsoid, making the resonant frequency range wider and the volume larger. To adapt to the changes in the structure of the sound box, the skin is stretched horizontally instead of vertically, the strings are appropriately thickened, and the neck is also changed from a round rod to an elliptical flat shape to prevent bending deformation caused by increased tension.
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