I'm looking for a MIDI player that shows each individual key's VOLUME.
I saw one online once that indicated this by the intensity of the COLOR of that key when it was depressed.
For example, in that particular MIDI program, when C5 (or any key) was pressed it became filled with dots of a certain color, such as red. In the instance of a piano, or any instrument where there is a decay, the key would fill with more dots at the beginning. These colored dots would diminish in number as the sound decayed. If the key was released then they would immediately go to 0.
In other words there would be more colored dots filling the key the louder the sound for that particular key was at that point in time. If the key wasn't pressed, or if the sound had decayed completely, then there would be no colored dots.
I wish I could remember the name of this MIDI player!