transposing keyboards

In music, contrivances of various sorts to shift the manuals of keyboard instruments so that the music played becomes automatically higher or lower, saving the players from learning to transpose at sight (see transposition). Such keyboards appeared on some organs as early as the 16th century and later on Ruckers harpsichords. Several inventions of the kind were made for the piano late in the 18th century and throughout the 19th century.