There are several different versions of the historical origin of the Yellow Bell and the exact meaning that it has. Accounts of the length and diameter are not exact and ironically (we are after all, talking about a length of tube that is going to define a dynasty) the measurements referred to can't be pinned down as exact quantities as the actual units are not known. As you can see from the following accounts, one has an exact date and the next says the date cannot be authenticated.
However, the general idea of a fundamental tone that relates to societies place in the cosmic order and the idea that this tone should be adjusted from time to time is present throughout. Sifting through the different accounts gives one the idea that pinning down the exact details of such a concept is perhaps not only a waste of time but a misdirected effort. For my own purposes it is enough to have found the Yellow Bell legend and realized its importance in helping to define my musical direction.
Like the OM in India, the sound of all sounds, the beginning of creation was also seen by the Chinese as the Primal Sound. The name given to the foundation tone of Chinese music, Huang Chung or 'yellow bell' referred not only to music but to the ruler and to divine power. The Huang Chung....was seen to be sacrosanct and not to be lightly tampered with. There was a deeply felt belief that any change to the Huang Chung would bring disaster to China itself. Yet, according to Yang Yin-liu, during the period from the thirteenth century B.C. to 1911 there were about thirty-five changes of pitches ranging from c' to a'. [Otto Karolyi 1998:146-148].
The earliest records giving mathematical ratios of musical intervals is the Lu Shih Ch'un Ch'iu (Chronicles of the House of Lu, c. 239 B. C.). This work described the construction of a set of twelve pitch pipes by the method of the cycle of fifths and tuned to the love song of a pair of phoenixes. This event was retrodated to the time of the legendary emperor Huang-ti and his musical minister Ling-Lun in the year calculated as 2698 B. C. [Needham and Robinson 1962:176-79]
There is no way to authenticate the date of the legendary event itself. However we do know that by the third century B. C. the practice of tuning court instruments to standard pitch pipes was well established. The ascription of this practice to Huang-ti in all likelihood set the precedent for restandardization of pitches, weights, and measures for each succeeding dynasty. From the third century B. C. onward, an important element of the state ideology was that music could influence the cosmic and social order. Peace and prosperity could be brought about by exhaustively locating all possible pitches by mathematical calculations and by performing music in tonalities appropriate to seasonal cycles. [Kuo-hang Han and Lindy Li Mark in Music of Many Cultures 1980: 11-12]
In the following account the term "kung" means tonic or fundamental note.
The Lu Shu (Book of Pitches) says that the volume of the Yellow Bell is 177,147 [unit unnamed]. The length is 9 inches. The kung of the Yellow Bell mode is the longest and is therefore called the fundamental tone, also the first tone. However, the so- called nine inches was not of the ordinary foot measure. It was derived from the human voice. The method for obtaining it was to let a person sing and make note of the lowest pitch. Then a tube of about 9 inches long and 0.9 inches in diameter was blown to match the voice. If the tube (tone) was higher than that of the voice, it was lengthened: if lower, then shortened. After alternating up and down, cutting the tube until it matched the human voice perfectly, that tube was designated the 9 inch Yellow Bell kung. [Ching Chou Pi Pien, in Ku Chin T'ushu Chi Ch'eng, vol. 91:620]