Science and Music , livre ebook

Science and Music
by Sir James Jeans

First published in 1937
This edition published by Rare Treasures
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Baghdad Museum
Fig. 1. Dancing to the lyre, and to the clapping ofcurved sticks (about 2700 B.C. ). From a royal tomb, Ur.

University Museum, Philadelphia
Fig. 2. Music from a four-stringed, bow-shaped harp (onright) and other instruments (about 2700 B.C. ). From the tombof Queen Shubad, Ur.
SUMERIAN MUSIC OF 4600 YEARS AGO
Science and Music



by Sir JAMES JEANS

O.M., M.A., D.Sc., Sc.D., D.L., LL.D., F.R.S.
To My Wife


[Pg ix]
PREFACE
Much has been added to our scientific knowledge of musicalsound, since Helmholtz published his great work Tonempfindungen in 1862. The new knowledge has been often andwell described, but mostly by scientists writing for scientistsin the technical language of science.
In the present book I have tried to describe the mainoutlines of such parts of science, both old and new, as arespecially related to the questions and problems of music,assuming no previous knowledge either of science or ofmathematics on the part of the reader. My aim has beento convey precise information in a simple non-technicalway, and I hope the subject-matter I have selected mayinterest the amateur, as well as the serious student, ofmusic.
I need hardly say that I am indebted to many friendsand books. A considerable fraction of my book is merelyHelmholtz modernised and rewritten in simple language.Another considerable fraction is drawn from the wealthof material provided in the notes added to Helmholtz'sbook by his English translator, A. J. Ellis. On the lesstechnical side, I have borrowed largely from Dayton C.Miller's book The Science of Musical Sounds (The MacmillanCompany, 1934), and am especially indebted to the authorfor permission to reproduce eleven excellent photographsof sound-curves. Among other sources from which I have [Pg x] drawn largely, and found especially valuable, I oughtto mention:
Sound by Lord Rayleigh (2 vols. Macmillan & Co.);
Sound by F. R. Watson (John Wiley, 1935);
A Text-book of Sound by A. B. Wood (Bell, 1932);
Hearing in Man and Animals by R. T. Beatty (Bell, 1932);
Physical Society of London : Report of a Discussion onAudition (1931);
Physical Society of London: Reports on Progress in Physics.Vol. II , 1935, and Vol. III , 1937;
Modern Acoustics by A. H. Davis (Bell, 1934);
The Acoustics of Orchestral Instruments and of the Organ byE. G. Richardson (Arnold, 1929);
The Acoustics of Buildings by A. H. Davis and G. W. C.Kaye (Bell, 1932);
Collected Papers on Acoustics by W. C. Sabine (HarvardUniversity Press, 1927);
as well as innumerable papers in technical and scientificjournals.
On the personal side, I am especially indebted to mywife, to Henry Willis and to Philip Pfaff, Mus. Bac.
J. H. JEANS Dorking June 1937
[Pg 1]
CHAPTER I INTRODUCTION
The Coming of Music
The lantern of science, throwing its light down the longcorridors of time, enables us to trace out the gradual evolutionof terrestrial life. Far away in the dim distances ofthe remote past we see it emerging from lowly beginnings—possiblysingle-cell organisms on the sea shore—andgradually increasing in complexity until it culminatesin the higher mammals of to-day, and in man, the mostcomplicated form of life which has so far emerged fromthe workshop of nature. And as living beings becomemore complex, they acquire an ever more intricate batteryof sense-organs which help them to find their way aboutthe world, to escape danger, to capture their food andavoid being themselves captured as food.
One of these is of special interest to musicians, for out ofit has developed our present organ of hearing. Sunk intothe skin of a fish, and running the whole length of its body,from head to tail on either side, there is a line of pits ordepressions. Under these lies an organ known as the"lateral-line" organ. This is believed to register differencesof pressure in the water, which will acquaint the fishwith the currents and eddies in which he is swimming,and may also warn him of the proximity of other fish,especially of large fish of hostile intentions.
Even the most primitive fishes seem to have possessed asimple organ of this kind. Gradually the depression nearest [Pg 2] to the head developed into something far more intricate,namely the hard bony structure known as the "labyrinth",which is found in all vertebrates, including ourselves. Itconsists of hollow tubes filled with fluid, and the main partof it is shaped so as to form three (or in rare cases only oneor two) semicircular canals, lying in directions mutuallyat right angles to one another, as on the right of fig. 1.

Fig. 1. The labyrinth of the left human ear (magnified about 5 times). Thethree semicircular canals are on the right ( d , e , f ) and the cochlea on theleft ( c ). a is the oval window to which the ear-drum transmits its vibrations; b is the round window, the function of which is explained below(p. 246).
When an animal turns its head or the upper partof its body, the fluid in the semicircular canals lagsbehind, because of its inertia, and so rubs over a setof paint-brushes of fine hairs, one in each canal; thebending of these hairs sends a series of nerve-impulses tothe brain, which inform it of the change of direction andinitiate a set of reflex actions to balance the change.Human beings are seldom conscious that they possess such [Pg 3] organs, although it is by their help that we regain ourbalance after a sudden slip. They are also responsible forthe giddiness we feel after spinning round too often or toorapidly, and for part at least of the even less agreeablesensations we experience when we are on a small ship ina turbulent sea.
A simple equipment of this kind would be adequate forprimaeval fish, which lived entirely in the water, but wouldsoon prove inadequate under new conditions which wereto come. For the geologists tell us of a period of greatdrought occurring some 300 million years ago, when seas,lakes and marshes were all drying up. It must have beenan anxious time for the fishes, many of which woulddesert their pools and shallows, and flop across dryland in the hope of finding new water. Clearly themore amphibious they could become, the greater wastheir chance of survival. In time some of the survivorsbecame pure land-animals—our own ancestry. Organs forregistering differences of pressure in water would be of littleuse to them now. What they needed was an organ toregister minute differences of pressure in air, for these wereassociated with sounds which might indicate the presenceof food or of danger, of friends or of enemies.
Gradually the required new organ seems to have developedout of the old. The story of the change providesone of the most fascinating—and, one is almost tempted tosay, most incredible—chapters in the evolutionary record.A small area of the bony structure of the labyrinth becamethinned down into a yielding membrane of mere skin, thinand soft enough to transmit variations of pressure from theair outside to the fluid within. At the same time, the [Pg 4] labyrinth itself grew in size and increased in complexity.That of the frog shews a small bulge, which, as we proceedfarther upwards in the scale of life, gradually developsinto the cochlea, which forms the essential part of the earof vertebrates. The external appearance of this wonderfullyintricate piece of apparatus is shewn in fig. 1 onp. 2; its interior is described later (p. 246). For themoment we can only compare it to the case, the sound-boardand the strings of a pianoforte of many strings—about3000 in birds, 16,000 in cats and 24,000 in man—allcompressed to the dimensions of less than a pea. Itenables its possessor not only to hear sounds, but also toanalyse them into their constituent tones. This power ofanalysis must obviously have had a great "survival value"for primitive life, since sounds which have been analysedcan be remembered, and those which have once beenfound to be associated with danger can be promptly actedupon when heard again—just as we do with the motor-hornin our less primitive life of to-day.
In some such way as this, the human race became possessedof its ears. At first they would merely be helps in thestruggle for existence. But we can imagine primitive manone day discovering in them an interest and a value ofanother kind; we can imagine him finding that the hearingof some simple sound, perhaps the twang of his bowstringor the blowing of the wind over a broken reed, was apleasure in itself. On that day music was born, and fromthat day to this innumerable workers of many ages and ofmany peoples have been trying to discover new sounds of apleasure-giving kind, and to master the art of blending andweaving these together so as to give the maximum of [Pg 5] enjoyment, with the result that music of one kind or anothernow figures largely in the lives of most civilised beings.
The Sense of Hearing
As life slowly climbed the long ladder of evolution, onesense after another arrived and developed. Hearing wasthe last to arrive, and the last to attain a state bordering onperfection. When it reached this state, the other senseswere already highly developed, and one, the sense ofseeing, had already attained too much importance to bedisplaced. For most animals seeing must always have beenmore important than hearing, and whether we think interms of our pleasure or of our well-being we must admitthat the same is true for us to-day; we would sooner loseany of our other senses than that of sight. Throughout mostof o