《音》是清末北京人徐鉴所编的一本蒙学韵书。文章简述了它在研究近代北音时较有价值的几个方面 ,比如提供了可供判断“尖团合流”下限期的语言事实和近代所发生的几次音变的有关状况 ,等等 “Tone ” is a book of Mongolian verses compiled by Xu Jian, a Beijing native of the late Qing dynasty. The article briefly describes several aspects which are more valuable when it comes to the study of modern northern sound. For example, it provides the linguistic facts that can be used to judge the lower limit of the “merging of the clumsy” and the status of several sound changes in modern times, etc.