Del Fandrich suggested that any insulating material will cut the sound coming from a piano. "Natural fiber... will be more effective..." Del's post: https://www.moypiano.com/ptg/pianotech.php/2001-September/093399.html The question of course would be where to put it. My wife's piano is a Mason & Hamlin AA (6'2") and is in a relatively small room. I have put two blankets above the strings and cut the volume significantly. The blankets are stiff enough that they never touch the strings. I have a piece of cardboard that keeps the material from touching the dampers. Something underneath the soundboard would help as well and as you have already been advised something insulating between the casters and the floor. Of course this kills the tone/overtones of the piano but it does cut the volume significantly. Brooks Weisman Arcata, CA
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