D O C U M E N T 2 9 7 J U L Y 1 9 2 2 2 2 9 Pray forgive my pressing you again.[3] Yours sincerely, Gilbert Murray Translator’s note: Original written in English. 297. From Richard Eisenmann Berlin N 24, 130 Friedrich St., 18 July 1922 Highly esteemed Professor, Allow me to express my thanks to you again for the honor of your visit and examination of my apparatus. No words need describe the gratification and satisfaction it gives me that they gained your approval. You wanted to be so kind as to give me a written report and opinion. For this I permit myself to submit the facts to you. The problem I posed for myself consisted in creating a device that makes feasi- ble the option of having piano tones continue to resound and swell as long as you like, with or without the hammer mechanism, by which each tone sounds immedi- ately and subsides rapidly. I wanted to make the forte-piano into a real piano-forte. The way I found the solution was to set the steel strings into constant resonant oscillations exactly synchronous with their eigenfrequencies by means of a pulsat- ing current from electromagnets. In the beginning I effected the synchronous current interruptions by means of tuning forks, tongues, or strings, but actually only theoretically. In 1889 I changed over to microphones, which had just been introduced at that time, which I rede- signed as contact breakers for my purposes. Although I obtained a very simple apparatus that way, it was insufficient. Only isolated tones indicated what could and must be achievable. One exemplar built this way is set up in the Deutsches Museum in Munich. For the rest, the apparatus was—and still is—composed of the contact-switch levers lying on top of the keys and a pedal that when pressed initially switches the current on and as it is pressed harder switches off resistances to intensify the cur- rent. The key-switches work likewise. It required very much thought and trials to design this to the satisfaction of the sensitive student pianist. Now he neither sees, nor hears, nor above all, feels it anymore. A decade ago I decided to use a rotating breaker instead of the inadequate micro- phones. Before I took the step of carrying this out, I viewed various systems in which motors are employed. At the Telegraph Testing Station I saw a very finely
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