4 The three primary colors of painters versus the seven colors of the spectrum

Louis-Bertrand Castel was the first to produce a pure color-tone analogy (from 1726 onward). He based his work on previous analogical models, including those of Aristotle, Kircher, and Newton. In contrast to his predecessors, however, his aim was not to provide proof of an all-encompassing global harmony, but to visualize music, that is, to substitute tones with colors. In order to circumvent or suspend the transience of music as a time-based art form, he wanted to combine it with painting, a spatial art, and so form a new art: musique muette. Castel argued that as music consisted of notes and painting of colors, an analogy between colors and musical notes would make it possible to visualize music, especially given that analogical reasoning was accepted as a scientific method. For the purposes of a practical implementation and in order to prove his theory, he designed a color organ, which he called the clavecin oculaire.

At that time, there were two established theories of color: Aguilonius’s and Newton’s. Also, at the beginning of the eighteenth century, Joseph Sauveur’s overtone series had provided a scientific explanation for the derivation of musical occurrences, while only four years earlier, in 1722, Jean-Philippe Rameau had declared the ecclesiastical modes — on which Newton’s work had been based — as definitively outdated and had identified the triad in a major key as the core of his new harmonic theory.

Thus, there were two fundamentally different systems available both for tones and for colors: a physics-based and an artistic model, respectively.

For colors, there was the sequence of colors in the spectrum, on the one hand, and the color scale used in painting, on the other. For tones, there was a physically based order — the overtone series — that corresponded to the spectrum and, again in correspondence to colors, there was the scale (representing the tone material or keys) used by composers.^[2]

Moreover, each given color and tone system consisted of subdivisions of different levels which all served as foundations for the compatibility required to form the analogies.

With regard to color, painters and dyers used a three-point scale, while physicians worked with a seven-point scale. These were sometimes modified to aid a potential correlation with tones. Thus, the three-point scale can be extended to six points by adding intermediate colors (yellow – orange – red – violet – blue – green) and to twelve points by inserting additional intermediate colors. The seven-point scale can be reduced to three points, given that the first five colors (red – orange – yellow – green – blue) contain the painters’ three primary colors in the order red – yellow – blue. For the extension of the seven-point scale into a twelve-point closed color circle, purple, which is not contained in the spectrum, must be added. Moreover, if a linear arrangement of the spectrum is to be maintained, when intermediate colors are added at regular intervals then a seven-point scale can only be extended to a thirteen-point scale. If a circular structure is sought, then a fourteen-point scale can be achieved. Thus, when the two color systems are combined, divisions based on the numbers 3 – 6 – 7 – 12 – 13 – 14 are possible.

Eighteenth-century music also had both a three-part and a seven-part structure: on the one hand, the major chord, which consisted of three tones and was derived from the overtone series and, on the other, the extension of this chord to a seven-tone major scale. The three- and seven-point musical scales could also be extended to twelve parts, which resulted in the chromatic scale. Hence, within music, divisions based on the numbers 3 – 7 – 12 are possible.

In the eighteenth century, then, the formation of analogies was based on divisions of 3 – 7 – 12, which were common to both systems. However, there were differences depending on the chosen starting point and the direction of the color scale.

In music, the initial starting point was the major as opposed to the minor mode and, within this, the key of C major. This form of allocation started with Castel (from 1726 onward) and was continued by Johann Gottlob Krüger who, like Castel, in 1743 had also designed a light organ (called the Farbenclavecymbel).

The most frequent analogy applied reduced the six possible combinations of the three primary painters’ colors to the combination contained from left to right in the spectrum: red – yellow – blue. This combination was correlated with the triad tones of the C-major chord, while a parallel was drawn between the remaining intermediate tones and the intermediate colors: c red, d orange, e yellow, f green, g blue, a indigo, b violet. Another way of arriving at the same analogy is to reduce Newton’s analogy between colors and tone intervals to an analogy between colors and tones, and to replace the Dorian scale used by Newton with the C-major scale. Hence, the physical and artistic derivations concur, which is why a clear separation between the two is not always possible, given that they tend to mutually confirm each other. Moreover, even after Newton, there was still no consensus with regard to the allocation of colors to tones. The diversity of these analogical models becomes evident when the variety of positions assigned on the scale to the color red, for example, is considered.