Musical keyboard

A musical keyboard is the set of adjacent depressible levers or keys on a musical instrument. Keyboards typically contain keys for playing the twelve notes of the Western musical scale, with a combination of larger, longer keys and smaller, shorter keys that repeats at the interval of an octave. Pressing a key on the keyboard makes the instrument produce sounds—either by mechanically striking a string or tine (acoustic and electric piano, clavichord), plucking a string (harpsichord), causing air to flow through a pipe organ, striking a bell (carillon), or activating an electronic circuit (synthesizer, digital piano, electronic keyboard). Since the most commonly encountered keyboard instrument is the piano, the keyboard layout is often referred to as the piano keyboard or simply piano keys.

The twelve notes of the Western musical scale are laid out with the lowest note on the left. The longer keys (for the seven "natural" notes of the C major scale: C, D, E, F, G, A, B) just forward. Because these keys were traditionally covered in ivory they are often called the white notes or white keys. The keys for the remaining five notes—which are not part of the C major scale—(i.e., C♯/D♭, D♯/E♭, F♯/G♭, G♯/A♭, A♯/B♭) (see Sharp and Flat) are raised and shorter. Because these keys receive less wear, they are often made of black colored wood and called the black notes or black keys. Black keys form a pentatonic scale. The entire pattern repeats at the interval of an octave.

The arrangement of longer keys for C major with intervening, shorter keys for the intermediate semitones date to the 15th century. Many keyboard instruments dating from before the nineteenth century, such as harpsichords and pipe organs, have a keyboard with the colours of the keys reversed: the white notes are made of ebony and the black notes are covered with softer white bone. A few electric and electronic instruments from the 1960s and subsequent decades have also done this; Vox's electronic organs of the 1960s, Farfisa's FAST portable organs, Hohner's Clavinet L, one version of the Korg Poly-800 synthesizer and Roland's digital harpsichords.

Some 1960s electronic organs used reverse colors or gray sharps or naturals to indicate the lower part (or parts) of a single keyboard divided into two parts, each controlling a different registration or sound. Such keyboards accommodate melody and contrasting accompaniment without the expense of a second manual, and were a regular feature in Spanish and some English organs of the renaissance and baroque eras. The break was between middle C and C-sharp, or outside of Iberia between B and C. Broken keyboards reappeared in 1842 with the harmonium, the split occurring at E4/F4.

The reverse-colored keys on Hammond organs such as the B3, C3 and A100 are latch-style radio buttons for selecting pre-set sounds.

The chromatic range (also called compass) of keyboard instruments has tended to increase. Harpsichords often extended over five octaves (>60 keys) in the 18th century, while most pianos manufactured since about 1870 have 88 keys. The lowest pitch (frequency: 27.5 Hz) of an 88-key piano is equivalent to a sub contrabass in the range name. Some modern pianos have even more notes (a Bösendorfer 290 "Imperial" has 97 keys, and a Stuart & Sons model has 108 keys). While modern synthesizer keyboards commonly have either 61, 76 or 88 keys, small MIDI controllers are available with 25 keys (digital systems allow shifting octaves, pitch, and "splitting" ranges dynamically, which, in some cases, reduce the need for dedicated keys. However, smaller keyboards will typically limit which musical scores can be played). Organs normally have 61 keys per manual, though some spinet models have 44 or 49. An organ pedalboard is a keyboard with long pedals played by the organist's feet. Pedalboards vary in size from 12 to 32 notes or 42 on a touring organ used by Cameron Carpenter.

In a typical keyboard layout, black note keys have uniform width, and white note keys have uniform width and uniform spacing at the front of the keyboard. In the larger gaps between the black keys, the width of the natural notes C, D and E differ slightly from the width of keys F, G, A and B. This allows close to uniform spacing of 12 keys per octave while maintaining uniformity of seven "natural" keys per octave.

Over the last three hundred years, the octave span distance found on historical keyboard instruments (organs, virginals, clavichords, harpsichords, and pianos) has ranged from as little as 125 mm (4.9 in) to as much as 170 mm (6.7 in).^{[citation needed]} Modern piano keyboards ordinarily have an octave span of 164–165 mm (6.46–6.50 in), resulting in the width of black keys averaging 13.7 mm (0.54 in) and white keys about 23.5 mm (0.93 in) at the base, disregarding space between keys.