Very interesting, I am familiar with many of the concepts and steps in the evolution of equal temperament, but I was not familiar with this part of the story at

Very interesting, I am familiar with many of the concepts and steps in the evolution of equal temperament, but I was not familiar with this part of the story at all (although I have seen pictures or drawings of keyboards with multiple split black keys). And very new to me, understanding the source of the terms "bemol" and "becuadro" (the words in Spanish for "flat" and "natural" - natural as in a note that loses its alteration and goes back to its neither-flat-nor-sharp pitch). Will try to delve into this in more detail some day with more time available. Thanks!