the ocular harpsichord of louis-bertrand castel - Gewina

Castel's ocular harpsichord 23
From a modern point of view it is interesting that Castel also argued for the
possibility of an "auricular prism", which would be able to separate the different
notes of a musical chord, and which he fruitlessly tried to construct for some
time.^''
Castel's proposal of a colour music and an ocular harpsichord was greeted
enthusiastically in the Mercure de France by a M. Rondct, who gave some
concrete ad'vise concerning the actual construction of the harpsichord. He
suggested that one make as many coloured windows in the case of the instrument
as il had keys and place a strong light in the case. Normally the windows
would be covered by a screen, but when a key was pressed, the corresponding
screen would swing over and the lighted window would become visible. If
desired, all kinds of mirrors could increase the effect.^ (Rondct's enthusiasm
for the whole idea seems to have been so great that he was still defending the
instrument in 1755.^^) It is less clear how seriously Castel himself took the
problem of constructing a real ocular harpsichord. In his first article he wrote
that he wanted "in the style of Socrates, the demonstration to precede the
proposition and the construction of the thing ... since it is not as an artisan but
as a philosopher that I set out to demonstrate you this new art."^ Much later,
he remarked on this original period: "It was only an idea, and I had no intention
of executing it."" And indeed, just the effect of the prism seemed enough to
satisfy his chromatic appetite:
One day, when the sun was shining brightly, having shut all windows of a room and having
placed four or five prisms in front of some holes that I had made in the shutters, making them
turn incessantly, I watched on the opposite wall a moving tapestry which, without any other
concert of harmony, presented me with the most agreeable spectacle that I could remember
having ever seen or heard.^
harmony of flavours along Castel's lines. His major diatonic scale was: sour, bland, sweet, bitter,
sweet-and-sour, tart, hot. For scents he failed for want of a sufficiently refined terminology. See
Chouillet-Roche. "Clavecin oculaire", p. 165.
"/ft/rf., p. 463.
Mercure dc France. April 1726, pp. 650-660.
^"^ Ibid., April 1755, pp. ir>0-163.
//)((/., .November 1725, pp. 2554, 2561: "Je veux mcme, en stile de Socrate, que la demonstration
precede la proposition & la construction de la chose ... car ce n'est pas en artisan, mais en
Philosophc que j'ai entrcpris de vous dcmontrer ce nouvel art".
Ibid., July 1755, p. 147: "ce n'etoit en effel qu'une idee, & je n'avois nulle intention de
Texccuter."
Ibid., March 1726, p. 461: "Un jour ayant ferme toutes les fenctres d'une chambre que le
Soleil eclairoit. & mis aux trous que j'avois fails dans les volets quatre ou cinq prismes qu'on
faisoit tourner sans cesse, je vis sur la muraille opposee une tapisserie mouvante, qui sans autre
concert d'harmonic. me donna le plus agreable spectacle que je me souvienne d'avoir jamais vu ni