>And of course there is pressng all 88 keys on the MIDI piano at the same time. I would like to know what that sounds like on a real piano though.

The mute pedal on an upright/console piano works by situating the hammers closer to the strings; if you stomp on it hard enough, you can get it to jerk all of the hammers such that they actually hit the strings and get this "all 88 keys" noise. I don't recommend this if you care for the piano, though :)

(On a grand piano, IIRC the mute pedal instead either adjusts the position of the hammer to only hit 1-2 of the strings, instead of all 3, or it moves the felts to dampen the sound).