2 3 0 D O C U M E N T 2 9 7 J U L Y 1 9 2 2 crafted, neat engine system standing in the cellar while the experimenter had all the switch levers and meters right next to his seat on the second story. So I first designed the apparatus with this idea: Each of the 84 tones requires its own, dedi- cated, specifically designated breaker number. Besides that, tuning must be possi- ble. Each of the 12 tones (and their octaves) therefore requires its special breaker. Its exact adjustment is provided by a motor-driven cone that is fed with minimal friction. The lowest A requires 27.5 oscillations per second = 1,650 per minute. The breaker has a diameter of 6.5 centimeters. At 1,650 revolutions, a cone of the equally small diameter of 6.5 cm therefore suffices. The cone I currently have has a diameter of 14 to 28 cm because the first breakers had a diameter of 13 cm. I likewise superfluously have a 3 hp motor while one of ½ hp suffices, as it does not have to work much beyond the minor friction of the 12 breakers and setting the pace. Thus in its manufacture the entire apparatus is reduced to proportions slender enough to also be able to fit comfortably in a rear room of a middle-class apartment. Correctly adjusted spring action can prevent any shaking and loud noises. In order to achieve the goal of generating a fine, pure tone according to the method described here, I had to bridge a difficult obstacle. No engine runs absolutely con- stantly. And for my purposes not a single revolution more than planned is allowed. Otherwise the tones would immediately be out of tune. As there wasn’t any suitable regulator, I invented the pendulum regulator, which forces the motor to rotate with the precision of a chronometer. You had a look at this solution for yourself and it won your applause. Until this point, since the very first idea, I did everything with- out the least outside assistance, intellectual or material. Now the research is far enough along for a man with capital and initiative to apply it commercially, whereby I place at his disposal my thirty-six years of expe- rience. The regulator apparatus, owing to its simplicity and accuracy, will be easily introduced. And I am convinced that even the entire keyboard apparatus will very quickly develop into a necessity in musical life, once it has been demonstrated pub- licly a few times, as Arthur Schnabel once played it in my home. The human ear quickly becomes accustomed to it. The new tone melds the fullness and volume of an organ-like but metallic orchestral sound to the coldness of the keyboard, just as Franz von Liszt himself had already wished. In utmost respect, I sign as yours truly, Dr. Richard Eisenmann.