SOME COMMENTS ON PIPE MEASUREMENTS
We all accept that pipe measurements are a fundamental piece of technical evidence in organ research. What it less certain is what should be measured and how measuring is best affected. My concern in this note is with scale measurement - which is usually taken to mean pipe diameter.
In the first hundred years or so of organ journalism in britain, pipe scales were not often mentioned. When they were mentioned it was simply the diameter measurement of one pipe that was given - e.g. an Open Diapason was described as having a scale of 6'' at 8ft. C. This merely reflected the current practice of organ-builders from the late nineteenth century; see, for instance, the Gray & Davison metal pipe book, or occasional entries in the Jardine books in the English Organ Archive. This piece of information, the diameter of just one pipe, is, of course, meaningless on its own unless the octave ratio used in calculating the rest of the pipe series is known. (It is rather similar to being given the composition of a mixture at its bottom note; you are given no clue as to what is happening in the middle of the register.) The Victorians - and their sons and grandsons - were safe, however, because, we believe, they accepted the rationalisation commonly attributed to Töpfer - viz. an octave ratio of 1 : 1.682. This is frequently described by stating on which note above the given note the diameter is halved. In the case of the 1 : 1.682 ration, it is the seventeenth note; the pipe diameter at e' is half that at c°. This standard, having been almost universally accepted, was sanctified by the Freiberger tagung für deutsche Orgelkunst in 1926, and such a ration applied to a pipe diameter of 155.5mm at 8ft C gives what is termed 'Normal Scale'. Variations from this are sometimes used, and indicated by the wording 'halving on the 18th' of 'halving on the 16th note', etc., the former implying an octave ratio of 1 : 1.631, and the latter 1 ; 1.741. This was usually achieved, I think, by adding or subtracting, as the case may be, a note in the 1 : 1.682 series and does not, therefore, introduce a different scale graph.
Prior to the invasion of Töpfer's ideas, scales were thought of and constructed quite differently in this country. It is possible that organ-builders in the eighteenth century and early-nineteenth century used logarithms in their calculations but it is unlikely; a practical craftsman in a conservative trade would more likely stick to simple calculations, and as far as pipe scales are concerned this means using simple arithmetical ratios. Christhard Mahrenholz, in The Calculation of Organ Pipe Scales from the Middle Ages to the Mid 19th century, (English translation by Andrew H Williams, published by Positif Press, Oxford, 1975), provides a very useful source of information here, although, of course, it does not draw on the English experience. In the little bit of 'surface' that I have 'scratched', the octave ratios I have found to have been used by English organ-builders in the late eighteenth and early nineteenth centuries have been largely 1:2 or 3:5, the former always with some addition constant to make it workable. The latter, which Mahrenholz describes as having been used frequently in North German organ-building, is the nearest simple ratio in organ-building to Töpfer's 1:8 (3:5 = 1 : 1.667). To my present knowledge, it was used in the early part of the nineteenth century by Elliott, and also Renn, and I shall not be surprised if it had become general practice by the time Töpfer was all the rage. What I'm suggesting is that as far as English organ-building is concerned, Töpfer was probably little more that a convenient 'modern' name applied to existing practice, just as the use of Vogler's name in connection with action layout was rather loose.
One important difference between English practice and Continental practice was the note on which a scale was laid. Hopkins (1) gives the clue to the English practice; 'Organ-builders are frequently heard to speak of an Open Diapason being made to a 12, 13, 14 or 15-inch scale, s the case may be. These figure refer to the width of the sheet of metal out of which the gamut G pipe is made...' Two important points emerge from this: gamut G (i.e. 5 1/3-ft G) is the starting point, not 8-ft C; and, perhaps too obvious, the plate (substantially the circumference of the pipe) is the initial measurement. The measuring of G pipes, therefore, is more useful that that of F# pipes, and circumference measurements are more useful than diameter measurements.
Circumference measurements can be done very conveniently by wrapping a strip of tracing paper around the body of a pipe and marking off the point of meeting. I first heard about this from Gerard Verloop of Shagen, Holland, and first saw it practised by Martin Goetze and Dominic Gwynn; I thereafter totally abandoned calipers. The advantages are several: you ave a permanent record of th a pipe's circumference; you leave the actual application of the ruler till later when you ave better light and less cramped conditions than usually obtain in the average organ interior; and it is possible to measure convincingly down to 0.2mm (which is equivalent to a diameter measurement of 0.06mm). The actual results will be close to original measurements, though a little larger, owing to (a) expansion of the outer face when rolled into pipe-form, and, (b) the solder line. It must be remembered, also, that there was likely to be some error in the actual cutting-out operation, and that it was common practice amongst organ-builders to 'add a little bit' to whatever measurement was used.
It is desirable to take the measurements of at least one complete stop in an organ (i.e. every pipe) - usually the Great 8ft open Diapason; the rest of the chorus(es) will often relate to this one way or another, and it will normally be necessary to take only sample measurements from the other stops, say each C and G throughout the compass.
There are several problems connect with the tabulation of results and their interpretation which are exercising my thoughts very much lately but which I will not attempt to put to paper at present. I would welcome any ideas or experiences from other engaged in this sort of work.
Author's note; I am indebted to Dominic Gwynn who has given much thought to these matters and whose comments and suggestions I have found most useful and stimulating.
1. Hopkins and Rimbault; The Organ, (3rd edition), p. 157, paragraph 704.