Generalized keyboards are musical keyboards, a type of isomorphic keyboard, with regular, tile-like arrangements usually with rectangular or hexagonal keys, and were developed for performing music in different tunings. They were introduced by Robert Bosanquet in the 1870s, and since the 1960s Erv Wilson has developed new methods of using and expanding them, proposing keyboard layouts (and some notations) including any scale made of a single generator within an "octave" (or more generally, period) of any size.