The four parts in singing are soprano,alto,tenor and bass.

唱歌的四个声部是女、女低、和低。

In fact, they divided Heaven into four parts and each part is composed by septuple Primary Stars.

西七星奎、娄、胃、昂、、、形状如虎，称西宫为白虎。南的井、鬼、柳、星、张、翼、轸联为鸟形，称朱雀。