Zhōu Déqīng 周德清 (1277–1365), zì Tǐngzhāi 挺齋 (or Tíngzhāi 庭齋), of Gāoān 高安 in Lóngxīng 龍興 / Ruìzhōu 瑞州 (modern Jiāngxī). The principal Yuán-period yīnyùn (phonology) scholar for qǔ-writing. His magnum opus, the Zhōngyuán yīnyùn KR4j0090 (completed in Tàidìng jiǎzǐ / 1324), is the founding work of modern Mandarin phonology — the first rhyme-book to classify píngshēng into yīnyáng sub-tones and to drop the rùshēng category, instead distributing rùshēng characters into píngshǎngqù. The work was prepared for běiqǔ practice (the Yuán zájù tradition). CBDB 104040 with no recorded dates; standard reference works (Chinese encyclopedia entries) supply 1277–1365.