One of my friends insists that he can make a muted (but undamaged) key/chord sounds using some pedaling technique. Does anyone know what the technique is and how to do it?
On a normal piano, the left pedal is pressed to make the sound quieter. It does this by moving the whole hammer mechanism closer to the strings on most uprights, and often by moving the mechanism to one side on grands. thus it's less distance for the strike to take place.
On some pianos, there is a practice pedal, often the middle of three, which brings a piece of felt down onto the strings, damping them slightly. This pedal is lockable. With both pedals in operation, the sound is very quiet.
If you're used to an electronic piano, there will often only be a sustain pedal, as you can turn down the volume.
The sustain pedal can also be used (on a real piano) for a muting effect. You strike a chord, release the keys, and a split second after you release the keys you depress the sustain pedal. If done well, this produces a sforzando effect: the chord is initially loud but then echos on quietly. Takes practice.