the ocular harpsichord of louis-bertrand castel - Gewina

Castel's ocular harpsichord 33
Saint Thomas, and even for 200 applauding people on the 1st of January
1755.^ Again Castel gave no technical details, but the Explanation of the ocular
harpsichord also contains a report on this performance, and there the instrument
is said to have included coloured glass windows, illuminated from within by a
hundred wax candles. However, as Castel was said to have exclaimed after the
show "that this was not even a sketch, a beginning of it, so far was it from being
perfect,"^ it probably still involved only a model. It was the harpsichord's swan
song, as Castel died two years later.
The author of Castel's eloge in the Memoires de Trevoux bluntly stated that
Castel had fruitlessly spend the best part of his life trying to build the ocular
harpsichord. There was no denying that in the theory of colours Castel had
made "important discoveries from which the arts could profit," but the instrument
which he had succeeded in constructing had "neither fulfilled the project of
its author, nor satisfied the expectation of the public".^
Other harpsichord builders
However, there are still some descriptions of the ocular harpsichord to be found
after Castel's death, although they differ widely. In Saverien's Histoire des
progres de I'esprit humain dans les sciences exactes et dans les arts qui en
dependent, published in 1766, it says that the instrument "consists of a table on
which is put up a kind of theatre complete with decorations. In front of the
theatre is a keyboard, whose keys are connected with the decorations. When a
key is pressed, no sound is heard but a colour is seen, in such a way that chords
of colours are formed just like chords of notes."'^'*
In 1769 the painter Lemierre, in his didactic poem La peinture, gave this
versified description of the ocular harpsichord, built by "the industrious Castel,
who today is not knovra any more":
He [Castel] places on a buffet the silvery instrument,
Where the ingenious art of a mobile hand
Questions the ebony and harmonic ivory;
Mercure de France, July 1755, pp. 144-145.
Explanation, p. 13.
Cited in Esprit, saillies et singularites, p. xx: "des decouvertes importantes dont les arts
pourroient profiler ... n'a ni rempli le devis de I'auteur, ni satisfait I'attente du public".
Saverien, Histoire, p. 275: "C'est un instrument forme par une table sur laquelle est 61ev£e
une espece de theatre avec ses decorations. Sur le devant de cette table est un clavier, dont les
touches repondent a ces decorations. Lorsqu'on louche sur le clavier, on n'entend pas des sons,
mais on voit des couleurs; de sorte qu'on fait des accords de couleurs comme des accords de sons."