1915] on The Piano-Player— Scientific Aspects 390 



piano, greatly influences the character of the accelerating force im- 

 pressed on the hammer when regarded as a function of the time. 

 The operation of playing a note is thus divided into two periods. 

 At the end of the first period a support is withdrawn from the palet 

 which raises the hammer, and the latter becomes disconnected. In 

 the second period either the hammer may fly up freely and strike the 

 note, or the palet may again overtake it and drive it forwards. To 

 produce these different actions the variable forces applied to the 

 key of a piano must evidently be similar in character to the 

 " screw-back " and " following " strokes in billiards. It is, of course, 

 theoretically possible that the hammer may fly up and strike the 

 string during the first period, may rebound before the end of the 

 second period, and may then be projected against the string a second 

 time. The evidence I have obtained from outside sources seems to 

 be negative, but certain results that I have obtained seem to indicate 

 that this effect may occur in pneumatic playing. The mechanism of 

 the check action may be such as to prevent the hammer from 

 rebounding and thus striking the string twice when the action is at 

 rest, but yet it may be capable, when iu motion, of returning the 

 hammer to the string, after the fashion of a tennis or cricket ball 

 struck by a bat in motion, which would not rebound with sufficient 

 velocity if the bat remained stationary. But it is very difficult to 

 test this point. 



Another important point is that, as the driving force is appHed 

 close to the base of the hammer, considerable flexural vibrations are 

 liable to be set up in the shaft. These may probably differ in ampli- 

 tude and phase, according to whether the hammer is released during 

 the first or second period, and it is clear that the effects produced iu 

 striking the strino^ may depend on whether the shaft is bent forwards 

 or backwards at the instant of impact, and on the amount of bending, 

 if any. A difference in this respect would affect the tone-quality 

 of the note. 



Xow the bass and treble hammers of the piano differ considerably 

 in weight, and therefore also in inertia, and the intermediate hammers 

 vary in this respect continuously from one end of the scale to the 

 other. It follows that when different parts of a chord are operated on 

 by the same pneumatic tension, the treble notes will require less time 

 to be set in motion than the bass ones. A short sharp blow will thus 

 produce its greatest effect in the higher parts of the scale, while a 

 longer sustained blow, or an increasing blow, will drive the bass notes 

 forward with increased velocity even after the treble notes have been 

 released. 



When I first started these experiments, it appeared to me probable 

 that the effects thus obtainable would be small, and that a very 

 difficult effort would be required to produce them. The contrary 

 proves to be the case. A very slight touch of the finger on a con- 

 trolling lever mav produce differences so marked as to appear 



2 D 2 



