2. One person hand-weighs each of the key’s hammers to make sure the “touch” of the keys is even

Most pianists can tell if the “touch” of a piano is off, meaning they have to push harder on one key to reach the volume of the others (or vice-versa). Steinway workers meticulously test each key with small weights, then make small adjustments to the “action” (the mechanism between the keys and the hammers that strike the strings) and add proper counter-weights within the keys themselves to ensure an even “touch” across the entire keyboard.