Despite Xue Song's coming from a distinguished lineage, it was said that he paid no attention to property management and fell into poverty.
At that time, Xue was defending Yecheng for Shi Siming, and he, along with several other key Yan generals -- Tian Chengsi, Zhang Zhongzhi, and Li Huaixian—submitted to Tang.
The Tang imperial regime, then under the rule of Emperor Xuanzong's son Emperor Suzong, was hesitant to displace them in fear that they would start another rebellion, so at the urging of the general Pugu Huai'en, they were allowed to remain at their current posts, and Xue was made the military governor (jiedushi) of Zhaoyi Circuit (昭義, headquartered in modern Anyang, Henan), controlling the six prefectures around Yecheng.
It was said that Xue governed Zhaoyi Circuit effectively, and that the people were comforted after the lengthy warfare.
Tian took control of four of the six Zhaoyi prefectures, and the Tang imperial government retained control of the other two, eventually merging it with nearby Zelu Circuit (澤潞, headquartered in modern Changzhi, Shangxi) and maintaining the Zhaoyi name for the merged circuit.