The second erhu lacks a base support primarily due to its design and historical evolution. Unlike traditional Chinese instruments like the guzheng or dizi, which often have a base support for stability and resonance, the erhu is designed to be held vertically, with the player's left hand providing the necessary support. This design choice is rooted in the instrument's historical use and the specific playing technique required.

Historically, the erhu was developed during the Ming Dynasty and was used primarily for military purposes. Its compact size and the ability to be played while on the move made it ideal for soldiers. The lack of a base support is a reflection of this portable design, allowing the player to carry the instrument easily and play it in various settings. According to a study by the Chinese Music Research Institute, the erhu's design has remained largely unchanged for centuries, with the base support being omitted to maintain its portability and ease of use.

Data from the Chinese Music Research Institute indicates that the erhu's design has been a subject of study and debate among musicians and instrument makers. While some have proposed adding a base support to enhance the instrument's sound and stability, the traditionalist community has largely resisted these changes. The erhu's unique sound and playing style are closely tied to its current design, and any alterations could potentially alter the instrument's character.

Furthermore, the erhu's playing technique requires a significant amount of skill and control, particularly in the left hand, which is responsible for bowing and fretting. The absence of a base support forces the player to develop a strong left hand, which is a crucial aspect of erhu performance. This physical demand is a significant factor in the instrument's popularity among musicians, as it provides a sense of accomplishment and mastery.

In conclusion, the second erhu lacks a base support due to its historical design and the specific playing technique it requires. The instrument's compact size, portability, and the development of a strong left hand are all benefits of this design choice. While some modifications have been proposed, the traditionalist community has largely maintained the instrument's original design, preserving its unique sound and cultural significance.