The Zhonghu and the Gaohu are common doubles for Erhu players. The Gaohu is higher pitched and the Zhonghu is the alto version. The shape is a little larger than the erhu but he string technique is about the same. The Zhonghu produces music of a lower pitch. The shape of the resonator varies from circular to octagonal. The Zhonghu is a Chinese orchestral instrument and a solo instrument. It functions as a viola. Zhonghu is a Chinese orchestral instrument and a solo instrument. This instrument first appears after 1104 in the Song Dynasty.

Its structure is similar to Erhu. The two strings are tuned to a perfect fifth (G, D) and the size of the wooden drum is relatively larger than Erhu. Snakeskin covers one end of the drum. Bow hair is placed between the two strings. The absence of fingering board allows variety of music effects through variation of the strings' tension. However variations are not as distinct as Erhu and Gaohu due its low and mellow tone. As an alto instrument with a two-octave range, the type has a deep and gloomy tone. The zhonghu is commonly used in ensembles and accompaniments, and for solos as well.