Unlike a harpsichord or guitar where the string is plucked with a pliable pick, the hammer strikes the string much like a xzylaphone hammer or a bass drum hammer. A properly adjusted damper will not let the string ring after it has fallen back on the string. Also, a metallic buzzing may occur if the damper wire is too close to the adjacent string. The complex mechanism between each key and its complementary strings that activates the hammer and damper. Heavy means it takes a lot of force to produce a good volume.
Light can be good or bad, it takes very little force to produce a good volume.
A new or rebuilt piano may feel heavy until it is broken in. The iron frame to which the strings are attached. Also known as the harp, it enables the strings to bear enormous pressure. In most pianos, the tuning pins come out of the pinblock and pass through the plate, where the plate has a hole for each tuning pin. A frequent scenario with age is that the soundboard splits, producing visible splits, usually paralleling the bass bridge.