I would like to build an electro magnet capable of causing piano strings to vibrate without the strings being struck first. As long as the hammers are up, the strings would vibrate on their own accord. An E-bow, used by guitarist for the same purpose, will (sort of) work on a limited range on the piano - but on only one note at a time. I would like to build something that can be hung inside the piano, close to the strings, that covers a wide range of notes. Hopefully I would be able to silently depress the keys, lifting hammers on those keys only, and thus creating an infinitely sustained piano sound, but without the attack the hammer gives. Thanks!