Ответ от murom на форумклассике.
Из предисловия к книге:
The regular system of bars with which music has been familiar since the middle of the 17th century, was only in its infancy; still, in general terms it may be said that the use of bars was clearly a foreshadowing of the present system, that it has not been found necessary to alter the original barring, although in certain cases, dotted bars have been employed to make the difficult passages clearer for modern musician. The time-signatures present an arrangement that can hardly be made clear without supplementary signs, and accordingly these are among the very few additions made by the editors.
Time-Signatures. These have very little to do with the actual value of the contents of the bars, but they indicate rather the ratio of measurement. For the most part they are three in number - the barred semi-circle indicating generally, but not always, all the varieties of quadruple time, whether of eight, four, or two minims' value; the semicircle with a point in it, used for 6/2 and 3/2 time generally (for 3/1 time - i.e., with semibreves in the bar, the barred semi-circle
is used); and thirdly, the figure 3, indicating nearly always 6/4 or 3/4 time.
В то время была важна "квадратность-неквадратность" размера (т.е. чётное или нечётное число половиннных нот в такте), остальное считалось не слишком существенным. Размер фактически переменный, т.е. "гуляет", тактовая черта ставится там, где нужна явная сильная доля, а остальное на усмотрение исполнителя.
