Sòng xiānshēng 宋先生 (“Master Sòng”) is the otherwise unknown alchemical master under whose name the Liǎomíng piān 了明篇 KR5a0284 (DZ 272) is preserved. According to the preface to that work by his disciple Mào Rìxīn 毛日新 of Sānqú 三衢 (dated Qiándào 4 = 1168), Master Sòng claimed to have received the ZhōngLǚ 鍾呂 kǒujué 口訣 (oral formula) directly from the legendary Zhōnglí Quán in 1165 (“白日再過 / báirì zài guò — passing the place at midday a second time” — preface 1a; cf. also the opening Yùzhēn gē 遇真歌, 1a, dated yǐyǒu 乙酉 — Sòng Qiándào 1 = 1165, fourth month). Mào Rìxīn met Sòng shortly afterward in Jiāngsū, where he obtained the present collection. Beyond what is preserved in Mào’s preface, nothing further is recorded of Master Sòng — neither name, nor place of origin, nor lineage affiliation. The persona may be pseudonymous (a stand-in for a Sòng-period yǐnyì 隱逸 hermit), or may refer to an actual but unnamed Daoist of the Jiāngsū region.