Today’s keyboard size dates back to about 1880, not long after the time when Liszt and others were actively involved with manufacturers. Notable exceptions since then include a smaller keyboard (with narrower keys) specially made by Steinway & Sons for Josef Hofmann early last century. Written evidence provided by Steinway Hamburg to Prof Dr Christoph Wagner (founder and director of the Hanover Institute of Music Physiology, 1974-1993) in 1986 states that the Hofmann keyboard was 3.5 cm narrower than normal. This means an octave width of 16 cm (6.3 inches), 0.5 cm less than normal.  Copies of this original letter (in German) and and English translation are available here:  http://smallpianokeyboards.org/wp-content/uploads/2019/03/Steinway-letter-to-ChWagner_Hofmann-keyboard_1986_original.pdf and: http://smallpianokeyboards.org/wp-content/uploads/2019/03/Steinway_Wagner_Hofmann-keyboard_1986_engl2017.pdf. For further comments about these keyboards in relation to Hofmann’s hand span, go to: http://paskpiano.org/keyboard-history/. However there is other evidence that Hofmann also had a much smaller keyboard made during his performing career. See: http://dsstandardfoundation.org/piano-keyboards-of-the-past/

Other changes during the late 19th and early 20th centuries include the use of cast iron frames which led to an increase in string tension resulting in heavier and deeper action, the lengths of keys, the height of blacks over whites, and the vertical dip of the black and white keys. As the piano evolved, the need for standardisation increased as pianists (professional and amateur) started to travel outside their own communities, hence the ‘one size fits all’ approach that has prevailed over the last century.

‘The size of the piano also affected boys and girls differently. In the eighteenth century the piano had been no bigger than a harpsichord and often smaller. At the beginning of the nineteenth century, though – with pedals appearing at floor level, the keyboard expanding in both directions, and passages in octaves appearing regularly in the newest repertory – the piano suddenly became, for children who learned it, a daunting daily reminder of how far they had to go to measure up in the adult world. Children grow at different rates, and some grow into the piano earlier than others, but many more girls than boys have felt they would never have the instrument – or the part of the repertory created by big-handed men – within their reach. Since the instrument itself has been unyielding in size, the pianist’s seat has been the principal means of helping children, or players of different sizes generally, adapt to it.’  ….Parakilas et al., 1999, Piano Roles, p.151.

Dr Ralph Manchester has summarised the problem of the ‘one size fits all’ approach:

‘Musical instrument design has evolved over time, and that is part of the problem we now face. In most cases, the designers of those instruments were men (rather than women) who lived and worked a few decades to a few centuries ago, mainly in Europe. They were likely to design instruments that they could use and that would be favored by the majority of musicians back then, who were mostly male. Today, musicians comprise a more diverse group with far more women, relatively few persons of European descent, and more persons with various physical disabilities. Nonetheless, we still play instruments that were designed for a fairly homogenous group of performers.’ (Editorial, MPPA, Dec 2006.)

Since 1880, there has been an enormous increase in women undertaking tertiary level training with the aim of pursuing performing careers, as well as a dramatic growth in the number of piano students of Asian ethnicity. Women have hands approximately 15% smaller than men, and Asians have smaller hands than Caucasians. In addition, 20th century piano repertoire often requires larger hand spans than repertoire composed during the 17th to 19th centuries.