律乃天地之正气，人之中声也。律由声出，音以声生，礼曰∶声成文谓之音。音之数
五，律之数六，分阴分阳，则音以宫商角征羽分太少而为十，故音以应日；律以黄钟、太簇、
姑洗、蕤宾、夷则、无射为阳，是为六律，林钟、南吕、应钟、大吕、夹钟、仲吕为阴，是为六吕，
合而言之，是为十二律，故律以应辰。一律所生，各有五音，十二律而生六十音，因而六之，
六六三百六十音以当一岁之日，故曰律历之数，天地之道也。然律吕皆生于黄钟，而黄钟
为万事之本，一阳之律也。黄者土德之色，钟者气之所种，所以言其本也；律生于冬至，气
起于一阳，所以言其始也。故黄钟之声中而正，合德于土也；黄钟之音重而浊，发声于初
也。观康节先生冬至吟曰∶冬至子之半，天心无改移。一阳初起处，万物未生时。玄酒味
方淡，太音声正希。此言如不信，更请问庖牺。夫玄酒方淡，指天一之初生；太音正希，谓
黄钟之将起。知乎此，则知黄钟之为义矣。
欧阳子曰∶造律者以黍。一黍之广，积为分寸以着于度；一黍多少，积为圭合以着于
量；一黍铢两，积为轻重以着于权衡。三者皆起于黄钟，故曰万事之本。
郑世子曰∶夫度量权量，所以取法于黄钟者，盖贵其与天地之气相应也。朱子所谓与
先天图一般者，夫先天图者，河图雒书也。河图之位十，天地之体数也；雒书之位九，天地
之用数也。盖一切万事。不离阴阳。图书二义，则阴阳之道尽矣，是为律历之本原，数学之
鼻祖也，故古人 律之妙，惟此二种而已。一以纵黍之长为分，九分为寸，九寸为黄钟，九
而九之，得八十一分，取象雒书之九自相乘之数也，是为律本，此载于淮南子者。一以横
黍之广为分，十分为寸，十寸为黄钟，十而十之，得百分，取象河图之十自相乘之数也，是为
度母，此载于太史公者。二术虽异，其律则同，盖纵黍之八十一分，适当横黍之百分，而横
黍之广，适与纵黍之长相合耳，此河图之偶，雒书之奇，参伍错综而律度方备，诚天地自然
之妙，非由人力安排者也。二法之外，本无九十分为黄钟者，至于刘歆班固，乃以九十分为
黄钟，是又合于斜黍度者。推原其误，盖自京房始。房时去古未远，明知古法九分为寸，以
其布算颇烦，初学难晓，乃创为之法而变九为十，故前后汉志，皆云九寸。今人宗九寸不宗
余法者，惑于汉志之偏见耳。苟能变通而不惑于一偏，则纵横斜黍，皆合黄钟之律矣。
律是天地间的正气，也是人心中发出的中正之声。律由声音产生，音因声而生，《礼记》说：“声音经过组织形成文采，就称为音。”音的数量有五个（宫、商、角、徵、羽），律的数量有六个。将阴和阳分开，则五音分为“太”和“少”两种层级，共成十个音阶，所以音用来对应天数；六律以黄钟、太簇、姑洗、蕤宾、夷则、无射为阳，这称为六律；六吕以林钟、南吕、应钟、大吕、夹钟、仲吕为阴，这称为六吕。合起来说，就是十二律，所以律用来对应地支时辰。每一律都能生出五个音，十二律共生出六十个音，再乘以六，得到三百六十个音，来对应一年的天数，所以说律与历法的数理，体现了天地的规律。然而，律和吕都生于黄钟，而黄钟是万事的根本，是一阳初动的律管。黄代表土的德行颜色，钟代表气所种植的地方，所以称其为根本；律的产生始于冬至，阳气起于一阳初生之时，所以称其为开始。因此，黄钟的声音中正平和，与土的德行相合；黄钟的音调沉重浑厚，是在初始阶段发出的声音。看康节先生（邵雍）在冬至日的吟诗说道：“冬至子时的半刻，天心没有改变移动。一阳刚刚升起之处，万物尚未生长之时。玄酒的味道正淡，太音的正声正稀。如果这话你不相信，再去请问伏羲氏。”这里的“玄酒方淡”，指的是天一之气初生；“太音正希”，说的是黄钟之律即将兴起。明白了这一点，就知道黄钟的含义了。
欧阳修说：制定律管的人使用黍米。一粒黍米的宽度，累积起来成为分寸，以此确立长度标准；一粒黍米的重量，累积起来成为圭合，以此确立容量标准；一粒黍米的轻重，累积起来成为铢两，以此确立重量标准。这三者都起源于黄钟，所以称黄钟为万事的根本。
郑世子说：度量衡之所以取法于黄钟，是因为珍贵它与天地之气相应。正如朱熹所说，这与先天图是一样的。所谓先天图，就是河图洛书。河图的位数是十，这是天地的本体之数；洛书的位数是九，这是天地的作用之数。大概一切万事，都离不开阴阳。河图和洛书的两种含义，就把阴阳的道理讲尽了，这是律历的本原，也是数学的鼻祖。所以古人对律的奥妙，只在这两种方法而已。一种是用纵向排列的黍米长度作为分，九分为一寸，九寸为黄钟的长度，九自乘九次，得到八十一分，取象于洛书中九自相乘的数，这称为律本，记载于《淮南子》中。另一种是用横向排列的黍米宽度作为分，十分为一寸，十寸为黄钟的长度，十自乘十次，得到百分，取象于河图中十自相乘的数，这称为度母，记载于司马迁的《史记》中。这两种方法虽然不同，但律的本质是相同的，因为纵向黍米的八十一分，恰好相当于横向黍米的百分，而横向黍米的宽度，恰好与纵向黍米的长度相吻合。这是河图的偶数与洛书的奇数，相互交错错综，从而使律和度的标准完备，确实是天地自然的奥妙，并非由人力刻意安排。除了这两种方法之外，原本没有用九十分作为黄钟长度的说法。至于刘歆和班固，却用九十分作为黄钟的长度，这又是结合了斜向排列黍米的方法。推究其错误的根源，大概是从京房开始的。京房那个时代距离古代不远，他明知古法是九分为一寸，但因为他的布算过程颇为繁琐，初学者难以理解，于是创制了新法，把九改为十。所以前后《汉书·律历志》都说是九寸。现在人们尊崇九寸而不尊崇其他方法的人，是被《汉书》中的偏见所迷惑罢了。如果能够变通而不被某一偏颇的观点所束缚，那么纵向、横向、斜向排列的黍米，都符合黄钟的律管标准了。
Lü (Pitch-pipes) is the righteous qi (vital energy) of heaven and earth, and the central sound within humans. Lü arises from sound, and Yin (musical tones) is generated by sound. The *Book of Rites* states: "When sounds are organized into patterns, they are called Yin." There are five Yin tones (Gong, Shang, Jue, Zhi, Yu), and six Lü pitches. Dividing them into Yin and Yang, the five Yin tones are divided into 'Tai' (Greater) and 'Shao' (Lesser) categories, resulting in ten pitch levels; thus, Yin corresponds to the days (of a cycle). The six Lü (Yang pitches) are Huangzhong (Yellow Bell), Taicu (Great Cluster), Guxi (Thoroughly Cleaned), Ruibin (Guest of the Southern Palace), Yize (Punishment), and Wuyi (No Repentance); these are the Six Lü. The six Lv (Yin pitches) are Linzhong (Forest Bell), Nanlv (Southern Lv), Yingzhong (Responding Bell), Dailv (Great Lv), Jialv (Joined Lv), and Zhonglv (Central Lv); these are the Six Lv. Together, they form the Twelve Lü, so Lü corresponds to the Earthly Branches (time periods). Each Lü generates five Yin tones; the twelve Lü generate sixty Yin tones. Multiplied by six, this yields three hundred and sixty tones, corresponding to the days of a year. Thus, it is said that the mathematics of Lü and Li (Calendar) embody the Way of Heaven and Earth. However, both Lü and Lv originate from Huangzhong, which is the root of all things and the Lü of initial Yang. 'Huang' (Yellow) represents the color of the virtue of Earth; 'Zhong' (Bell) represents where qi is planted; hence it is called the root. Lü is born at the Winter Solstice, when qi begins with the emergence of one Yang line; hence it is called the beginning. Therefore, the sound of Huangzhong is central and upright, harmonizing with the virtue of Earth; its tone is heavy and mellow, emitted at the very beginning. Consider the poem by Mr. Kangjie (Shao Yong) on the Winter Solstice: "At the half-way point of Zi hour on Winter Solstice, the Heavenly Heart does not shift or move. At the place where one Yang first rises, when all things have not yet been born. The taste of Xuanjiu (dark wine) is just faint, the Zhengyin (correct sound) is just rare. If you do not believe this, go ask Fuxi again." Here, 'Xuanjiu is just faint' refers to the initial birth of Tianyi (Heaven One); 'Zhengyin is just rare' refers to the impending rise of Huangzhong. Understanding this reveals the meaning of Huangzhong.
Ouyang Xiu said: Those who created the Lü used millet grains. The width of one grain of millet accumulates to form cun and fen (units of length), establishing the standard for measurement; the weight of one grain of millet accumulates to form gui and he (units of volume), establishing the standard for capacity; the heaviness of one grain of millet accumulates to form zhu and liang (units of weight), establishing the standard for balance. These three originate from Huangzhong, hence it is called the root of all matters.
Prince Zheng said: The reason why measures of length, capacity, and weight take their model from Huangzhong is because it is valued for its correspondence with the qi of heaven and earth. As Zhu Xi stated, this is akin to the Xiantian Tu (Prior Heaven Diagram). The so-called Xiantian Tu is the Hetu (River Chart) and Luoshu (Lo River Map). The position number of Hetu is ten, representing the substantive numbers of heaven and earth; the position number of Luoshu is nine, representing the functional numbers of heaven and earth. Generally, all matters do not depart from Yin and Yang. The two meanings of Hetu and Luoshu exhaust the Dao of Yin and Yang; they are the origin of Lü and Li, and the ancestors of mathematics. Thus, the ancients considered the subtlety of Lü to lie only in these two methods. One method uses the length of longitudinally arranged millet grains as 'fen'; nine fen make one cun, and nine cun make the length of Huangzhong. Nine multiplied by itself nine times yields eighty-one fen, taking imagery from the number nine in Luoshu squared; this is called the Root of Lü, recorded in *Huainanzi*. The other method uses the width of transversely arranged millet grains as 'fen'; ten fen make one cun, and ten cun make the length of Huangzhong. Ten multiplied by itself ten times yields one hundred fen, taking imagery from the number ten in Hetu squared; this is called the Mother of Measurement, recorded in Sima Qian's *Records of the Grand Historian*. Although these two methods differ, the essence of Lü is the same. The eighty-one fen of longitudinal millet correspond exactly to the one hundred fen of transverse millet, and the width of transverse millet coincides exactly with the length of longitudinal millet. This is the interweaving of the even numbers of Hetu and the odd numbers of Luoshu, making the standards of Lü and measurement complete. It is truly the natural wonder of heaven and earth, not arranged by human effort. Outside these two methods, there was originally no concept of using ninety fen as the length of Huangzhong. Later, Liu Xin and Ban Gu used ninety fen as the length of Huangzhong, which combined the method of diagonally arranged millet grains. Tracing the error back to its source, it likely began with Jing Fang. Although Jing Fang lived close to ancient times and knew the ancient law was nine fen to an inch, his calculations were cumbersome and difficult for beginners to understand, so he invented a new method changing nine to ten. Consequently, both the *Book of Han* and *Later Book of Han* state nine cun. People today who revere the nine-cun standard over others are confused by the biased view in the *Book of Han*. If one could adapt and not be confined to a single bias, then longitudinal, transverse, and diagonal millet arrangements would all conform to the Lü of Huangzhong.