Yes , two categories : http://en.wikipedia.org/wiki/Isomorphic_keyboard http://en.wikipedia.org/wiki/Isomorphic_keyboard These tackle the problem of how the no

Yes , two categories : http://en.wikipedia.org/wiki/Isomorphic_keyboard http://en.wikipedia.org/wiki/Isomorphic_keyboard These tackle the problem of how the normal piano layout requires different motor-memories for the same interval-patterns at different pitches . Janko and Wicki-Hayden are examples , as is layout of the chromatic button accordion . http://en.wikipedia.org/wiki/Generalized_keyboard http://en.wikipedia.org/wiki/Generalized_keyboard These are designed to work for various other tunings than standard 12-tone tuning ; i think most of them map some pitch-space to a hexagonal grid .