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Que n'ont ils tous Employés leurs tems à la même Machine.

(If only they had all occupied their time on the same machine.)

Not on display

Order image © All images subject to copyright

Artist or maker

Saint-Aubin, Charles-Germain de (b.1721, d.1786)


1740-c 1757

The drawing depicts the model of ocular harpsichord that Castel exhibited in 1730. However, he worked on this and other versions until his death in 1757.

Place of production

  • Paris, France


  • watercolour, ink and graphite on paper

Type of object

  • drawings

Accession number


One of a set, see others ▸

A white haired cleric dressed in a black cassock and a four-peaked biretta with a tassel on top sits at a slim keyboard instrument with cork-screw legs. He is shown in right profile. While his hands press down on keys from the lower of its two keyboards, his left foot pumps a long pedal to which a pulley system has been attached. The pulley system, which passes through the body of the instrument, appears to activate the release of liquid from a large syringe mounted on top of its soundboard. The arc of water squirted by the syringe is traced with a dotted line: it splashes down onto the face of the seated man. He looks straight ahead at a line of seven upright planks of various heights inserted into the instrument. Each is differently coloured and inscribed with one of the sol-fa syllables. Behind them on the soundboard of the instrument are seven mushroom-shaped pads. A painter's pallet, bowsaw, scroll, musical score, set-square and measuring stick are gathered at his feet.


Curatorial commentary

  • Charles-Germain de Saint-Aubin's drawing shows the Jesuit physicist Louis-Bertrand Castel performing on his ocular harpsichord, or “clavecin optique”, as Castel called his invention (Johnson, 2012). Castel designed the instrument to demonstrate his widely published theories about the analogous relationship of colour and pitch, which were first published in the “Mercure de France” in November 1725. Discussions of synaethesia went back to Antiquity. These had been revived from the Renaissance onwards, and were explored by Isaac Newton (from whom Castel claimed inspiration). The bizarre instrument caused great interest in the philosophical community and among the general public. Although it also met with ridicule (as here), Castel’s prolific writings kept the idea of an ocular harpsichord in the public mind through to his death in 1757 – the period from which this drawing probably dates.
  • Castel never completed a definitive version of the harpsichord, but worked on it for decades, in spite of constant protests that, as philosopher and mathematician, he was unequipped to construct it himself. Castel’s tools lie in confusion at his feet. The present drawing shows the model that Castel first exhibited in 1730. The harpsichord operated on one octave. Pressure on the keys caused slips of coloured paper to be raised into view. A later model, of 1755, replaced the coloured paper with stained glass panels illuminated by candles.
  • Rosalind Holmes Duffy (personal communication, 2010) has suggested that Castel persevered with the project in the face of public derision because he enjoyed the celebrity it attained. Although he hoped to make his name with more elevated achievements, he could not bear to share with anyone else the attention that his harpsichord enjoyed, even if another individual might have been able to accomplish its construction.
  • The enema syringe spraying Castel as he sits at his keyboard shows the value that Charles-Germain perceived the instrument to have. While Castel thinks the machine will impress the public and give him stature, every time he depresses the pedal he is actually making himself ridiculous.
  • In the inscription, Charles-Germain, whose anti-Jesuit sentiments are widely displayed in the “Livre de Caricatures” (e.g. 675.277, 675.354) expresses the wish the rest of his order had engaged in such harmless if ridiculous pursuits.
Physical description

Dimensions (mm) / weight (mg)

187 x 132


la [?], [mi], [do], mi, fa, sol
Inscribed, probably by Charles-Germain de Saint-Aubin, on coloured boards mounted on soundboard.

Que n'ont ils tous Employés leurs tems à la même Machine. / Le Pere Castel.
Inscribed by Charles-Germain de Saint-Aubin, below image, in ink

raport des Sons et des Couleurs.
Inscribed by Charles-Germain de Saint-Aubin, after first inscription, in ink

Top left corner, in bracket, in ink

Translation of inscription

If only they had all occupied their time on the same machine. Father Castel.
Relationship of sounds and colours




Part of

  • Livre de Caricatures tant bonnes que mauvaises. 675.1-389


  • Waddesdon (National Trust)
  • Bequest of James de Rothschild, 1957


  • James H. Johnson; Musical culture; Colin Jones, Juliet Carey, Emily Richardson, The Saint-Aubin Livre de caricatures: drawing satire in eighteenth-century Paris, Oxford, SVEC, 2012; 215-232; pp. 222-3, fig. 9.5
  • Katie Scott; Saint-Aubin's jokes and their relation to...; Colin Jones, Juliet Carey, Emily Richardson, The Saint-Aubin Livre de caricatures: drawing satire in eighteenth-century Paris, Oxford, SVEC, 2012; 349-403; p. 388n

Related literature

  • Mercure de France (1721-1791); Geneva; Slatkine Reprints; 1968-1974
  • Louis-Bertrand Castel; Esprit, sallies et singularitiés du Père Castel; Paris; Vincent; 1763
  • Wilton Mason, Father Castel and his Color Clavecin, The Journal of Aesthetics and Art Criticism, xvii, September 1958, 103-16
  • Maarten Franssen, The ocular harpsichord of Louis-Bertrand Castel and the science and aesthetics of an eighteenth-century cause célèbre, Tractix: Yearbook for the History of Science, Medicine, Technology and Mathematics, iii, 1991, 15-77
  • Thomas Hankins, The Ocular Harpsichord of Louis-Bertrand Castel; Or The Instrument that Wasn't, Osiris, ix, 1994, 141-56

Related files

Other details

Subject person and role

  • Louis-Bertrand Castel, Pictured
  • Louis-Bertrand Castel, Named in text