Under the heading “Special Keyboards” are such instruments which cannot be classified in an obvious way in the larger main groups of stringed keyboard instruments and harmoniums together with their self-playing variants.
It is a motley collection with a wide range, from a strange experimental piano with resonant strings, which probably dates from the 1760s, to the two electric organs from the 1950s and 1970s, which may represent a paradigm shift from acoustic to electronic instruments.