A piano keyboard is the row of white and black keys on a piano which, when pushed by the fingers, cause small hammers to hit tightly stretched metal strings inside the piano and thereby create sound. The keyboards on almost all modern acoustic pianos contain 88 keys, each a step on the chromatic scale. 52 of these keys are white and 36 are black, with a basic pattern repeating every twelve keys of W-B-W-B-W-W-B-W-B-W-B-W. The black keys are slightly thinner than the white keys and are also substantially shorter, not extending to the outer edge of the keyboard. This arrangement of lengths, widths and colors facilitates playing the piano with limited, or even no, viewing of the keyboard and thereby allows the performer to instead focus on reading the sheet music.
Spanning slightly more than seven octaves, these 88 keys produce pitches ranging from lower than the lowest that can be produced by a contrabassoon to the highest that can played on a piccolo. Pressing a key causes a padded hammer to strike several of the 230 stretched wires. The hammer rebounds from the wires, which continue to vibrate at their resonant frequency. These vibrations are transmitted through a bridge to a soundboard that amplifies the sound. When the key is released, a damper stops the wires' vibration. In contrast to the keyboards on pipe organ and the harpsichord, which were already in widespread use before the piano was invented (around 1700), volume can be controlled according to how forcefully the keys are pressed.