Isomorphic keyboard

An isomorphic keyboard is a musical input device consisting of a two-dimensional grid of note-controlling elements (such as buttons or keys) on which any given sequence and/or combination of musical intervals has the "same shape" on the keyboard wherever it occurs – within a key, across keys, across octaves, and across tunings.

Fig. 1: The Wicki isomorphic keyboard note-layout, invented by Kaspar Wicki in 1896