Beethoven's "feel the music" synth

I was in the music store today and was trying out some digital piano's. One room was very noisy and the built in sound on the digital piano was turned as loud as it would go. It had decent base which on this compact model was positioned near the keys and one could easily feel the sound through the keys. I was surprised at how much the feedback through my fingers added to the "music connection". So.. my idea is to convey the sound through vibration of the keys to the players fingers. A seperate "power of feedback" control would be handy as you might want to turn it low/off for other reasons e.g. such as it making some amount of unwanted noise itself when you are using headphones trying to be quiet.