A set of levers (keys) actuating the mechanism of a musical instrument such as the organ, harpsichord, clavichord, piano etc. It probably originated in the Greek hydraulis. Its influence on Western musical systems was great: the primacy of the C major scale is partly due to its being played on the white keys, and the 12-semitone chromatic scale could also be derived from the keyboard's design.
Up to the 13th century, keyboards were diatonic with a C as first key, except for the inclusion of B♭ which permitted transpositions compressing the compass of plainchant to less than two octaves. By the early 14th century, the development of polyphony had caused a widening of compass and the addition of chromatic notes. The arrangement of the keys in two rows, with the sharps and flats grouped by two and three in the upper, existed by the early 15th century. A compass F-a″ was frequent by the 16th, and in Italy upper limits of c‴ or even f‴ were common. The compass increased further in the 17th century, and reached five octaves by 1700. Pianos now usually cover seven octaves and a 3rd, A″-c‴′ : organ keyboards rarely cover more than five octaves.
In the 18th and 19th centuries, keyboard instruments gained a leading position in European musical practice, which led to attempts to provide many types of instrument with a keyboard mechanism (e.g. the harmonium and celesta). Electronic technology has led to many adaptations of the conventional keyboard, including split and staggered manuals and touch-sensitive keyboard. Experimental keyboards include the ‘sequential keyboard’ (1834), the reversed keyboard (1876) and the Enharmonic keyboard. See
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