What is the difference between the Hydraulous’ (water organ) and modern keyboards? I know that they existed a long time ago in the Greek civilization. What was the first asymmetrical layout keyboard, and how did it change with the Hydraulous. Modern keyboards seem too appropriate to fingering melodies, and touching any music. They seem irreplaceable. I like to know about specific historical events. Thank you.
Because pictures of the hydraulis show only white keys, this question may be asking when black keys were first used. Well, then:
The earliest organ keyboards... had seven notes for each octave... like the white keys of a piano. However new notes were added to this simple 'diatonic' scale. By 1300 the familiar scale of twelve semitones was already developed and instrument builders were faced with the problem of desigining keys such that twelve could be controlled in the span of a hand. One solution was to use typewriter-like stud keys mounted in two rows. Other makers used split keys similar to the ones on the piano and this became the preferred system.
G. Hindley, Keyboards, cranks, and communication: the musical mindset of western technology. Icon, vol. 3 (1997), pp. 167-180.