The pronunciation of each homophone group is given by a fanqie formula, a pair of common characters respectively indicating the initial and final sounds of the syllable.
Lu Fayan's work was very influential, and led to a series of expanded and corrected versions following the same structure, the most important of which is the Guangyun (1007–08).
[3][4] Karlgren believed that the Qieyun system (represented by the Guangyun) reflected the standard speech of the Sui-Tang capital Chang'an (modern Xi'an), which spread across the empire except for Fujian.
Since the discovery of an early copy of the Qieyun in 1947, most scholars believe the dictionary reflects a combination of reading pronunciation standards from the capitals of the late Northern and Southern dynasties period.
[5] Karlgren's transcription involved a large number of consonants and vowels, many of them very unevenly distributed; indeed he disdained phonemic analysis as a "craze".
[6] His notation, based on Johan August Lundell's Swedish Dialect Alphabet, went through several revisions from his Études sur la phonologie chinoise (1915–1926) through to the Compendium of Phonetics in Ancient and Archaic Chinese (1954).
[10][11] In the early 1970s, Li Fang-Kuei used an amended version of Karlgren's transcription as a point of departure for his reconstruction of Old Chinese phonology.