404 Professor G. H. Bryan [March 19, 



different kinds of touch obtainable by the use of different muscles. 

 But really my experiments with a piano-player have led to results 

 which seem to indicate that Mathay may be right after all. 



What makes the whole question more difficult to understand is 

 that the causes producing all these different effects must be capable 

 of being represented by differences in the shape of a single graph. 

 If we take, for example, a piano key pressed down by a finger, then 

 there are a large number of quantities associated with the blow, which 

 are recognized in elementary dynamics. These include the time from 

 the instant the finger touched the key, the distance the key has 

 descended, the velocity of the key, its acceleration, the pressure of the 

 finger on the key, the momentum communicated, the energy or work 

 done in depression. But the principles of dynamics tell us that if we 

 draw the graph connecting tiuo of these variables, the relations 

 between any other two are fully determined. Differences in the 

 elasticity or tenseness of any particular set of muscles can only affect 

 the shape of this graph. In pneumatic playing the same is evidently 

 the case. And yet such differences do seem to influence the result. 



Although I have been trying for a long time past to account 

 theoretically for the observed effects, the results are still far short 

 of finality. It is clear that neither Helmholtz's nor Kaufmann's 

 mathematical investigations fully suffice for the purpose. There are, 

 however, other difficulties. One is that, although it is easy to 

 observe differences of effect which are, as a rule, quite conspicuous, 

 it is not so easy to define exactly in what these differences consist. 

 Again, the success of a piano-player as a musical instrument largely 

 arises from the fact that the manipulation of the various controls, 

 both for tempo and expression, soon becomes intuitive. A great 

 deal evidently depends on the elasticity of the muscles of the hands 

 and feet. It would be very difficult to ascertain precisely the effect 

 of differences in this elasticity on the tension in the playing pneu- 

 matics while a note is being sounded. In short, while my early 

 attempts at getting improved results with a piano-player were based 

 on dynamical considerations, it appears probable that a complete 

 dynamical theory of the observed effects will involve investigations 

 of no small degree of difficulty. But those who have experience of 

 such matters will probably understand that a still more difficult task 

 arose when it was sought to develop and apply the device for 

 practical purposes. The mere engineering of this control device 

 into a form in which it can easily be adapted to any internally fitted 

 player without interfering with the use of the piano for hand- 

 playing, has given a great deal of trouble to the Motomusic Company, 

 and the process of obtaining evidence from independent sources as 

 to how far the results obtained in different hands justify our claims, 

 still involves work strictly experimental in character for which it is 

 difficult to obtain opportunities in the early stages of an invention. 



