206 Professor Silvanus P. Thompson [June 13, 



WEEKLY EVENING MEETING, 

 Friday, June 13, 1890. 



Sir James Crichton Browne, M.D. LL.D. F.R.S. Treasurer 

 and Vice-President, in tlie Chair. 



Professor Silvanus P. Thompson, D.Sc. MM.L 



The Physical Foundation of Music. 



Something in the constitution of the human mind impels us to 

 search, to examine, to analyse. Even music^ — the art which appeals 

 above all to the emotions — cannot remain exempt. We receive the 

 impression on our senses, and forthwith are impelled to the enquiry : 

 Why does this move us ? How can the mere movement or tremor of 

 the air enter thus into our senses ? The instinct to analyse will not 

 let us alone until we have found some sort of an explanation — a 

 mental resting-place — enabling us to account to ourselves for the 

 things that would otherwise seem an inscrutable mystery. 



Now, in music, there are three main questions for which in this 

 way an answer has been sought : — 



(1) Why is it that the ear is pleased by a succession of sounds 

 belonging to a certain particular set called a scale ? 



(2) Why is it that when two (or more) musical sounds are 

 simultaneously sounded, the ear finds some combinations agreeable 

 and others disagreeable ? 



(3) Why is it that a note sounded on a musical instrument of 

 one sort is different from, and is distinguishable from, the same note 

 sounded with equal loudness upon an instrument of another sort ? 



In brief, we desire to know the origin of melody, the cause of 

 harmony, and the nature of timbre. 



The theories which have been framed to account for each of 

 these three features of music are based on a double foundation — 

 partly physical, partly physiological. With the physiological aspect 

 of this foundation we have to-night nothing to do, being concerned 

 only with the physical aspect. What, then, are the physical founda- 

 tions of melody, of harmony, and of timbre? Demonstrable by 

 experiment they must be, in common with all other physical facts, 

 otherwse they cannot be accepted as proven. What are the facts, 

 and how can they be demonstrated ? 



To Pythagoras and the Greeks it was known that the notes of the 

 melodic scale corresponded in a curiously- perfect way to certain 

 numerical relations between the lengths of the stretched strings. 

 Modern research has transferred these numerical relations to the 

 frequency of the vibrations executed by the moving body, and pitch 

 is now a matter assignable in definite numbers. In the philosophical 



