'Phags-pa script
The phonology of Old Mandarin is most clearly defined in the "Zhongyuan Yinyun". The 'Phags-pa script and the "Menggu Ziyun" tend to retain more traditional elements, but are useful in filling in the spartan description of the "Zhongyuan Yinyun". The language shows many of the features characteristic of modern Mandarin dialects, such as the reduction and disappearance of final stop consonants and the reorganization of the Middle Chinese tones.