Experimental musical instrument including intonarumori ("intoners" or "noise machines"), to create "noises" for performance. Unfortunately, none of his original intonarumori survived World War II. Replicas are being made though. Léon Theremin was a Russian inventor, most famous for his invention of the theremin around 1919–1920, one of the first electronic musical instruments. The Ondes Martenot is another early example of an electronic musical instrument. The luthéal is a type of prepared piano created by George Cloetens in the late 1890s and used by Maurice Ravel in his "Tzigane" for luthéal and violin. The instrument can produce sounds like a guitar or a harmonica,
Theory of forms experience because the forms are not in the physical world. Therefore, our real knowledge of the forms must be the memory of our initial acquaintance with the forms in heaven. Therefore, what we seem to learn is in fact just remembering. No one has ever seen a perfect circle, nor a perfectly straight line, yet everyone knows what a circle and a straight line are. Plato utilizes the tool-maker's blueprint as evidence that Forms are real:... when a man has discovered the instrument which is naturally adapted to each work, he must express this natural form, and not others which